Using InfoFind for Unit Conversion

Searching for a Unit

Conversions Formulas

Metric Unit Prefixes

Time Notes

Temperature Notes

Additional Notes

Writing Guide

Calculation Uncertainty with InfoFind and other Unit Conversion Programs

References

Positive Numbers | Negative Numbers | ||||
---|---|---|---|---|---|

Factor | Name | Symbol | Factor | Name | Symbol |

10^{24} |
yotta | Y | 10^{-1} |
deci | d |

10^{21} |
zetta | Z | 10^{-2} |
centi | c |

10^{18} |
exa | E | 10^{-3} |
milli | m |

10^{15} |
peta | P | 10^{-6} |
micro | µ |

10^{12} |
tera | T | 10^{-9} |
nano | n |

10^{9} |
giga | G | 10^{-12} |
pico | p |

10^{6} |
mega | M | 10^{-15} |
femto | g |

10^{3} |
kilo | k | 10^{-18} |
atto | a |

10^{2} |
hecto | h | 10^{-21} |
zepto | z |

10^{1} |
deka or deca | da | 10^{-24} |
yocto | y |

Factor | Name | Symbol |
---|---|---|

2^{80} |
yotta | Y |

2^{70} |
zetta | Z |

2^{60} |
exa | E |

2^{50} |
peta | P |

2^{40} |
tera | T |

2^{30} |
giga | G |

2^{20} |
mega | M |

2^{10} |
kilo | K |

International standards organizations are opposed to the industry's description of standard prefixes. Because of this, they have tried to introduce there own binary prefix names and apply the decimal based SI prefix to the current terms. To make matters even more confusing, hardware manufactures are now often displaying the size of hard drives and computer storage with Metric Prefixes while computer memory and software programs use the Binary Prefix. InfoFind displays the most common binary and decimal (Metric) prefixes used in the Computer Category. InfoFind displays the additional items when you uncheck [Show Only Common Units].

**Julian calendar:**The Julian calendar was a solar calendar introduced by the Roman Emperor Julius Caesar in 46 B.C. to replace the Roman calendar. The Roman calendar was a lunisolar calendar but it was maintained by corrupt politicians who would add or remove days from the calendar as they wanted so it became inaccurate for farming and for festivals. In the Julian calendar a common year is defined to comprise 365 days, and every forth year is a leap year comprising 366 days. The Julian calendar was superseded by the Gregorian calendar.**Gregorian calendar:**The Gregorian calendar was introduced by Pope Gregory XIII in 1582 to replace the Julian calendar; and the Gregorian calendar is the calendar now used as the civil calendar in most countries. The Gregorian calendar differs only slightly from the Julian calendar and was introduced because over time differences had accumulated compared to the actual solar time period so Easter was occurring before the Vernal Equinox. Like the Julian calendar in the Gregorian calendar a common year is defined to comprise 365 days, and leap years comprising of 366 days; but in the Gregorian calendar every year that is exactly divisible by four is a leap year, except for centurial years, which must be divisible by 400 to be leap years. Thus, 2000 is a leap year, but 1900 and 2100 are not leap years.**Astronomical time periods:**Normally we use the Gregorian calendar and time intervals such as seconds, minutes, or hours to tell time; but in the study of astronomy there are additional time periods. One of the reasons for this is because the earth orbits around the sun in an ellipse rather then a circle so there are different measures for calculating astronomical time periods. InfoFind includes calculations for several astronomical time periods. They are listed below but can be difficult to understand at first. For a more detailed understanding of astronomical time periods, you may want to read a book or web site with pictures and examples on this topic. NASA's web site (http://www.nasa.gov/) provides a lot of great resources.**Sidereal (fixed star to fixed star):**The measure of the rotation of the earth (or another planet) in relation to the stars, rather than the sun.**Tropical or Solar (equinox to equinox):**The measure of one revolution of the earth around the sun, with respect to the vernal equinox. The vernal equinox occurs in the spring time when the sun passes over the equator.**Synodical or Lunar (new moon to new moon):**The time interval between similar configurations in the orbit. A synodical month for earth is the time between repeated lunar phases, such as new moon to new moon.**Anomalistic (perigee to perigee):**An anomalistic month for earth is the average period of revolution of the moon from perigee to perigee. Perigee is the orbital point when the moon is closest to the earth. An anomalistic year for earth is the period of one revolution around the sun from perihelion to perihelion. Perihelion is the point in solar orbit when the earth is closest to the sun.**Draconic Month (node to node):**A draconic month is the time from required for the moon to move from an orbital node back to the same node. A node is one of the two points of intersection of the orbit of the moon with the plane of the orbit of the earth.**Eclipse Year (node to node):**The interval between two successive conjunctions of the sun with the same node of the moon's orbit.

**Planetary Notes:**InfoFind includes time values for known planets in our solar system.**Length of Day:**It is the average time in hours for the sun to move from the noon position in the sky at a point on the equator back to the same position. For earth this is the 24 hour day.**Sidereal Rotation Period:**The time it takes for a planet to complete one rotation relative to the fixed background stars. For earth this equals the sidereal day.**Sidereal Orbit Period:**The time it takes the planet to make one revolution around the Sun relative to the fixed stars. For earth this equals the sidereal year.**Tropical Orbit Period:**The time for the planet to make one revolution around the Sun from one point in its seasonal orbit to the equivalent point (e.g. equinox to equinox). For earth this equals the tropical year.

- Centigrade is an obsolete term and approximately equal to the degree Celsius. InfoFind includes Centigrade because it used in older publications and writings. When calculating with Centigrade InfoFind will list the result as ‘‘approximately’’.

**Formatting:**Units in InfoFind are generally formatted as ‘‘unit name (alternate spellings) (alternate symbol) (symbol)’’. For example, meter is spelled in the U.S. as meter but some countries spell it as metre. The symbol for meter is ‘‘m’’ so InfoFind displays the entry for meter as ‘‘meter (metre) (m)’’.**Regional Units:**InfoFind includes specific units from many countries. These countries include Canada, Hong Kong, India, Japan, Korea, Taiwan, U.S., and U.K. Generally, if InfoFind lists a country with a unit then the country will be listed in brackets. For example the Korean unit of area pyong is listed as ‘‘pyong (Korea)’’.**Spelling:**The spelling of English-language words - for example, ‘‘meter,’’ ‘‘liter,’’ and ‘‘deka’’ are usually used instead of ‘‘metre,’’ ‘‘litre,’’ and ‘‘deca’’. This spelling also reflects recommended United States practice.**Older Units:**InfoFind includes a number of older units because they are often referred to in older publications and writings. Some of the units will have the terms archaic or obsolete written next to the unit name in brackets. For example degree centigrade is listed as ‘‘degree centigrade (obsolete)’’. Generally, InfoFind applies the term archaic to units that are no longer used, and obsolete to units that have been replaced.**Volume:**The primary unit of volume is the cubic meter (m³) and may be used to express the volume of any substance, whether solid, liquid, or gas. The liter (L) is a special name for the cubic decimeter (dm³) but it is not recommended that the liter not be used to give the results of high accuracy measurements of volumes. Also, it is not common practice to use the liter to express the volumes of solids nor to use multiples of the liter such as the kiloliter (kL).**Symbols:**Several symbols that cannot be displayed on all computers so they are substituted on the unit conversion form.- The unit ohm in Electric Resistance is defined having the symbol but InfoFind shows the symbol as ohm (the name of the unit). When ohm is written in documents the symbol should be used.
- The unit gamma in Magnetic Flux Density is defined having the symbol but InfoFind does not show the symbol. When gamma is written in documents the symbol should be used.
- For the unit type Pressure several units include water calculations; the correct symbol for water is H
_{2}O, but InfoFind cannot display the lowered 2 on all computers so H2O is used instead.

**Blood Alcohol Concentration (BAC):**In many countries BAC is calculated as ‘‘weight by volumne’’ and calculated as ‘‘1 gram per 1 deciliter of blood’’ or ‘‘1 milligram per 1 milliliter’’. However different countries use different calculations or different methods of determining BAC. The two most common methods of BAC are listed in the category ‘‘Mass Density or Concentration’’.**Astronomical Unit:**The unit astronomical unit of length can have it's symbol written as AU or ua. AU is the most common symbol used for this unit type. Astronomical unit is equal to the mean distance of the earth from the sun (about 92.95 million miles).**Unified Atomic Mass Unit:**In some fields such as biochemistry the unified atomic mass unit is called the dalton, symbol Da; however, this name and symbol are not accepted by international standards organizations. Similarly, AMU is not considered an acceptable unit symbol for the unified atomic mass unit. The only recommended name is ‘‘unified atomic mass unit’’ and the only recommended symbol is u. However InfoFind displays this unit with all alternate spellings and symbols because all are widely used. The unified atomic mass unit is defined as equal to 1/12 of the mass of an unbound atom of the nuclide carbon-12.**Mathematical Formulas in Unit Symbols:**InfoFind includes a lot of different unit categories so many of the units are derived from primary units and include mathematical formulas in the unit symbol. For example, area derives from length. The primary metric unit for length is a meter (m), so the primary metric unit for the derived unit of area is square meter (m²). The 2 in m² is an exponent so m² is a math formula. Some units in InfoFind have powers larger then 3 so the symbol ‘‘^N’’ is used to indicate an exponent. Another example of a derived unit type with math formulas is speed, which derives from time and length. A common unit of speed is kilometer per hour (km/h). The symbol km/h is a math formula because this unit of speed is calculated by dividing length by time. With the previous example the symbol / is used for division. Additional math symbols used in InfoFind are * for multiplication, and ‘‘^-N’’ for negative exponents.

**Overview:**This deals primarily with the International System of Units (SI) but most of the rules also apply to Imperial Units. Some of these items refer to proper spelling in the United States but most rules apply to all countries.**Overall clarity in writing:**The primary goal in writing units is overall clarity to avoid confusion about what is being written. This brief guide covers a number of recommend practices that allows for clarity in writing.**References:**All references are listed at the end of this document. The main sources for the writing guide are the International des Poids et Mesures (BIPM) (http://www.bipm.fr/) and the National Institute of Standards and Technology (http://www.nist.gov/).**Abbreviations:**Because acceptable units generally have internationally recognized symbols and names, it is not permissible to use abbreviations for their unit symbols or names, such as sec (for either s or second), cc (for either cm^{3}or cubic centimeter), or mps (for either m/s or meter per second), should be avoided and only standard unit symbols, SI prefix symbols, unit names, and SI prefixes should be used.**Unacceptability of unit symbols and unit names together:**Unit symbols and unit names are not mixed and mathematical operations are not applied to unit names.

Examples:kg/m3, kg • m3, or kilogram per cubic meter but not kilogram/m3, kg/cubic meter, kilogram/cubic meter, kg per m3, or kilogram per meter3 **Plurals:**Unit symbols are unaltered in the plural.

Example:75 cm but not: 75 cms **Typeface and spacing:**Unit symbols are printed in roman (upright) type regardless of the type used in the surrounding text, and are attached to unit symbols without a space between the prefix symbol and the unit symbol. This last rule also applies to prefixes attached to unit names.

Examples:mL (milliliter) pm (picometer) GV (gigaohm) THz (terahertz) **Capitalization:**The unit symbols Y (yotta), Z (zetta), E (exa), P (peta), T (tera), G (giga), and M (mega) are printed in upper-case letters while all other unit symbols are printed in lower-case letters except that: (a) the symbol or the first letter of the symbol is an upper-case letter when the name of the unit is derived from the name of a person; and (b) the recommended symbol for the liter in the United States is L.

Examples:m (meter) s (second) V (volt) Pa (pascal) lm (lumen) Wb (weber) **Liter:**The alternative symbol for the liter, L, was adopted in order to avoid the risk of confusion between the letter l and the number 1. Thus, although both l and L are internationally accepted symbols for the liter, to avoid this risk the symbol to be used in the United States is L.**Punctuation:**Unit symbols are not followed by a period unless at the end of a sentence.

Example:‘‘Its length is 75 cm.’’ or ‘‘It is 75 cm long.’’ but not: ‘‘It is 75 cm. long.’’ **Clarity in writing values of quantities:**The value of a quantity is expressed as the product of a number and a unit. Thus, to avoid possible confusion, values of quantities must be written so that it is completely clear to which unit symbols the numerical values of the quantities belong. Also to avoid possible confusion, it is strongly recommended that the word ‘‘to’’ be used to indicate a range of values for a quantity instead of a range dash (that is, a long hyphen) because the dash could be misinterpreted as a minus sign.

Examples:51 mm X 51 mm X 25 mm but not: 51 X 51 X 25 mm ‘‘225 nm to 2400 nm’’ or ‘‘(225 to 2400) nm’’ but not: 225 to 2400 nm ‘‘0 °C to 100 °C’’ or ‘‘(0 to 100) °C’’ but not: 0 °C - 100 °C ‘‘0 V to 5 V’’ or ‘‘(0 to 5) V’’ but not: 0 - 5 V (8.2, 9.0, 9.5, 9.8, 10.0) GHz but not: 8.2, 9.0, 9.5, 9.8, 10.0 GHz ‘‘63.2 m ± 0.1 m’’ or ‘‘(63.2 ± 0.1) m’’ but not: ‘‘63.2 ± 0.1 m’’ or ‘‘63.2 m ± 0.1’’ ‘‘129 s - 3 s = 126 s’’ or ‘‘(129 - 3) s = 126 s’’ but not: 129 - 3 s = 126 s **Arabic numerals:**Values of quantities are expressed in acceptable units using Arabic numerals and the symbols for the units.

Examples:m = 5 kg but not: ‘‘m = five kilograms’’ or ‘‘m = five kg’’ the current was 15 A but not: the current was 15 amperes. **Writing a value with a unit symbol:**There is a space between the numerical value and unit symbol, even when the value is used in an adjectival sense, except in the case of superscript units for plane angle.

Examples:a 25 kg sphere but not: a 25-kg sphere an angle of 2°3'4" but not: an angle of 2 °3 '4 " **Spelling unit names with prefixes:**When the name of a unit containing a prefix is spelled out, no space or hyphen is used between the prefix and unit name.

Examples:milligram but not: milli-gram kilopascal but not: kilo-pascal **Weight:**When the word ‘‘weight’’ is used, the intended meaning is clear. (In science and technology, weight is a force, for which the SI unit is the newton; in commerce and everyday use, weight is usually a synonym for mass, for which the SI unit is the kilogram.) In scientific and technical writings the word ‘‘mass’’ should be used instead of ‘‘weight’’. In any case, in order to avoid confusion, whenever the word ‘‘weight’’ is used, it should be made clear which meaning is intended.**Unit symbols obtained by multiplication:**Symbols for units formed from other units by multiplication are indicated by means of either a half-high (that is, centered) dot •, a star character *, cross (that is, multiplication sign) X, or a space. The half-high dot is preferred in most cases because it is less likely to lead to confusion. If the half-high dot is not available (example, when typing on some computers) then the star character is preferred.

Examples:‘‘N•m’’ or ‘‘N m’’ **Multiplying Numbers:**When the dot is used as the decimal marker as in the United States, the preferred sign for the multiplication of numbers or values of quantities is a cross (that is, multiplication sign) (X), not a half-high (that is, centered) dot (•).

Examples:25 X 60.5 but not: 25 • 60.5 53 m/s X 10.2 s but not: 53 m/s • 10.2 s 15 X 72 kg but not: 15 • 72 kg **Unit symbols obtained by division:**Symbols for units formed from other units by division are indicated by means of a solidus (oblique stroke, /), a horizontal line, or negative exponents.

Examples:m/s or m s or m*s ^{-1}m/s ^{2}or m*s^{-2}but not: m/s/s **Unacceptability of compound prefixes:**Compound prefix symbols, that is, prefix symbols formed by combining two or more prefix symbols, are not permitted. This rule also applies to compound prefixes.

Examples:nm (nanometer) but not: mmm (millimicrometer) 1026 kg = 1 mg (1 milligram) but not: 1026 kg = 1 mkg (1 microkilogram) **Use of multiple prefixes:**In a derived unit formed by division, the use of a prefix symbol (or a prefix) in both the numerator and the denominator may cause confusion. Thus, for example, 10 kV/mm is acceptable, but 10 MV/m is often considered preferable because it contains only one prefix symbol and it is in the numerator. In a derived unit formed by multiplication, the use of more than one prefix symbol (or more than one prefix) may also cause confusion. Thus, for example, 10 MV • ms is acceptable, but 10 kV • s is often considered preferable. However, such considerations usually do not apply if the derived unit involves the kilogram. For example, 0.13 mmol/g is not considered preferable to 0.13 mol/kg.**Prefixes with the degree Celsius and units accepted for use with the SI:**Prefix symbols may be used with the unit symbol °C and prefixes may be used with the unit name ‘‘degree Celsius.’’ For example, 12 m°C (12 millidegrees Celsius) is acceptable. However, to avoid confusion, prefix symbols (and prefixes) are not used with the time - related unit symbols (names) min (minute), h (hour), d (day); nor with the angle-related symbols (names) ° (degree), ' (minute), and " (second). Prefix symbols (and prefixes) may be used with the unit symbols (names) L (liter), t (metric ton), eV (electronvolt), and u (unified atomic mass unit). However, although submultiples of the liter such as mL (milliliter) and dL (deciliter) are in common use, multiples of the liter such as kL (kiloliter) and ML (megaliter) are not. Similarly, although multiples of the metric ton such as kt (kilometric ton) are commonly used, submultiples such as mt (millimetric ton), which is equal to the kilogram (kg), are not. Examples of the use of prefix symbols with eV and u are 80 MeV (80 megaelectronvolts) and 15 nu (15 nanounified atomic mass units).**Symbols for numbers and units versus spelled-out names of numbers and units:**Key elements of a scientific or technical paper, particularly the results of measurements and the values of quantities that influence the measurements, should be presented in a way that is as independent of language as possible. This will allow the paper to be understood by as broad an audience as possible, including readers with limited knowledge of English. Thus, to promote the comprehension of quantitative information in general and its broad understandability in particular, values of quantities should be expressed in acceptable units using

— the Arabic symbols for numbers, that is, the Arabic numerals, not the spelled-out names of the Arabic numerals; and

— the symbols for the units, not the spelled-out names of the units.

Examples:the length of the laser is 5 m but not: the length of the laser is five meters the sample was annealed at a temperature of 955 K for 12 h but not: the sample was annealed at a temperature of 955 kelvins for 12 hours - If the intended audience for a publication is unlikely to be familiar with a particular unit symbol, it should be defined when first used.
- Because the use of the spelled-out name of an Arabic numeral with a unit symbol can cause confusion, such combinations must strictly be avoided. For example, one should never write ‘‘the length of the laser is five m.’’

**Unacceptability of stand-alone unit symbols:**Symbols for units are never used without numerical values or quantity symbols (they are not abbreviations).

Examples:there are 106 mm in 1 km but not: there are many mm in a km it is sold by the cubic meter but not: it is sold by the m ^{3}**%, percentage by, fraction:**When the internationally recognized symbol % (percent) for the number 0.01 is used, a space is left between the symbol % and the number by which it is multiplied. Further, the symbol % should be used, not the name ‘‘percent.’’

Examples:xB = 0.0025 = 0.25 % but not: ‘‘xB = 0.0025 = 0.25%’’ or ‘‘xB = 0.25 percent’’ **Names of numbers:**Because the names of numbers 109 and larger are not uniform worldwide, it is best that they be avoided entirely for scientific writing (in most countries, 1 billion = 1*1012, not 1*109 as in the United States); the preferred way of expressing large numbers is to use powers of 10.**Roman numerals:**It is unacceptable to use Roman numerals to express the values of quantities. In particular, one should not use C, M, and MM as substitutes for 10^{2}, 10^{3}, and 10^{6}, respectively.**Proper names of quotient quantities:**Derived quantities formed from other quantities by division are written using the words ‘‘divided by’’ rather than the words ‘‘per unit’’ in order to avoid the appearance of associating a particular unit with the derived quantity.

Examples:pressure is force divided by area but not: pressure is force per unit area **Spelling unit names raised to powers:**When the names of units raised to powers are spelled out, modifiers such as ‘‘squared’’ or ‘‘cubed’’ are used and are placed after the unit name.

Example: meter per second squared (m/s2)

The modifiers ‘‘square’’ or ‘‘cubic’’ may, however, be placed before the unit name in the case of area or volume.

Examples:square centimeter (cm ^{2})cubic millimeter (mm ^{3})ampere per square meter (A/m ^{2})kilogram per cubic meter (kg/m ^{3})**Decimal sign or marker:**The recommended decimal sign or marker for use in the United States is the dot on the line. For numbers less than one, a zero is written before the decimal marker. For example, 0.25 s is the correct form, not .25 s.**Grouping digits:**Because the comma is widely used as the decimal marker outside the United States, it should not be used to separate digits into groups of three. Instead, digits should be separated into groups of three, counting from the decimal marker towards the left and right, by the use of a thin, fixed space. However, this practice is not usually followed for numbers having only four digits on either side of the decimal marker except when uniformity in a table is desired. Also, the practice of using a space to group digits is not usually followed in certain specialized applications, such as engineering drawings and financial statements.

Examples:76 483 522 is preferred to: 76,483,522 43 279.168 29 is preferred to: 43,279.168 29 8012 or 8 012 is preferred to: 8,012 0.491 722 3 is preferred to: 0.4917223 0.5947 or 0.594 7 is preferred to: 0.59 47 8012.5947 or 8 012.594 7 is preferred to: 8 012.5947 or 8012.594 7 **Additional usage and questions:**In the United States questions concerning the more fundamental aspects of the SI and subtle aspects of proper SI usage should be directed to the National Institute of Standards and Technology (http://www.nist.gov/). Outside of the United States the Bureau International des Poids et Mesures (BIPM) in France (http://www.bipm.fr/) has resources in many languages to help understand the SI.

Bureau International des Poids et Mesures (BIPM) (France)The International System of Units (SI), 7th Edition, 1998 |

National Institute of Standards and Technology (NIST) (US)NIST Special Publication 811, 1995 Edition NIST Special Publication 330 NIST Technical Note 1297 NIST Household Weights and Measures NIST Special Publication 447 |

National Aeronautics and Space Administration (NASA) (US)Planetary Fact Sheet Solar System Exploration Calendars and Their History SP-7012, Physical Constants and Conversion Factors, Second Edition Dictionary of Technical Terms for Aerospace use |

United States Naval Observatory (Department of the Navy) (US)The Astronomical Almanac for the Year 2007, (ISBN: 0-11-887337-7) |

Center of the International Cooperation for Computerization (CICC) (Japan)Data Book of Cultural Convention in Asian Countries |

Government Information Office (GIO) Republic of China (Taiwan)The Republic of China Yearbook - Taiwan 2002 Appendix VII. Weights and Measures in Use in the ROC Weights and Measures in Use in Taiwan |

Taiwan External Trade Development Council (TAITRA) (Taiwan)Unit of Measurement |

Department of Justice, Bilingual Laws Information System (Hong Kong)Chapter 68, Weights and Measures Ordinance Schedule 1, Definitions of Units of Measurement, 6/30/1997 |

Astronomical Society of South Australia (Australia)Easter Dating Method |

Library of Congress (US)Pinyin Conversion Project, New Chinese Romanization Guidelines |

Environmental Protection Agency (EPA) (US)EPA's Radiation Protection Program: Radiation Glossary EPA's Radiation Protection Program: Understanding Radiation |

The 2005 World Exposition, Aichi (Japan)Measurement Conversion Table |

Statistics Bureau (Japan)Outline of the 2000 Population Census of Japan, Explanation of Terms |

Microsoft (US)Microsoft® Computer Dictionary, Fifth Edition (ISBN: 0-7356-1495-4) |

International Electrotechnical Commission (IEC) (Switzerland)60027-2 Ed. 2.0 (2000-11) |

U.S. Metric Association (USMA) (US)Metric usage and metrication in other countries Non-SI Units |

National Association of State, Departments of Agriculture (NASDA) (US)Conversion Table |

Massachusetts Institute of Technology (MIT) (US)Acronyms and Abbreviations Used at MIT |

National Highway Traffic Safety Administration (NHTSA) (US)Computing a BAC Estimate |