UnitsConverter

Scientific Sources & References

UnitsConverter.io is built on authoritative scientific and technical standards. This page lists all primary sources used to compile our conversion factors and unit definitions. Every conversion factor has been verified against these official sources.

Primary Standards Bodies

BIPM (Bureau International des Poids et Mesures)

The International Bureau of Weights and Measures — the official body responsible for defining the International System of Units (SI).

Used for:

  • SI base units (meter, kilogram, second, ampere, kelvin, mole, candela)
  • SI derived units (newton, pascal, joule, watt, hertz, etc.)
  • Metric prefixes (kilo, mega, giga, milli, micro, nano, etc.)
  • Official SI definitions and conversion factors

Latest SI Brochure (9th edition, 2019) and official updates

NIST (National Institute of Standards and Technology)

The U.S. federal agency that maintains and promotes measurement standards and related technology.

Used for:

  • US customary units (inch, foot, mile, pound, gallon, etc.)
  • Imperial units (commonly used in the UK and other countries)
  • Exact conversion factors between US customary and metric units
  • Official US measurement standards

NIST Special Publication 330 (The International System of Units) and official conversion tables

ISO (International Organization for Standardization)

The international body for developing standards that ensure quality, safety, and efficiency across industries.

Used for:

  • Fuel consumption units (km/L, L/100km, MPG, etc.) — ISO 80000-9
  • Quantities and units standards — ISO 80000 series
  • Industrial and specialized measurement conversions
  • International engineering standards

ISO 80000 series (Quantities and Units) and related standards

IEC (International Electrotechnical Commission)

The international standards and conformity assessment body for electrical, electronic, and related technologies.

Used for:

  • Data storage units (byte, kilobyte, megabyte, gigabyte, etc.)
  • Binary (IEC 60027-2) and decimal data storage standards
  • Data transfer rates (bits per second)
  • Computer and information technology measurements

IEC 60027-2 (Letter symbols to be used in electrical technology) and related standards

Unit Category References

Length & Distance

  • BIPM SI Brochure (meter definition)
  • NIST inch-to-metric conversion (exact: 1 inch = 2.54 cm)
  • ISO 80000-3 (Quantities and units — Space and time)

Mass & Weight

  • BIPM SI Brochure (kilogram definition)
  • NIST avoirdupois pound definition (1 lb = 453.59237 g exact)
  • ISO 80000-4 (Quantities and units — Mechanics)

Temperature

  • BIPM SI Brochure (kelvin definition)
  • NIST temperature scale definitions and conversions
  • ITS-90 (International Temperature Scale of 1990)

Volume & Capacity

  • BIPM SI Brochure (liter definition: 1 L = 1 dm³)
  • NIST US liquid gallon definition
  • ISO 80000-3 (Quantities and units)

Speed & Velocity

  • BIPM SI Brochure (meter and second definitions)
  • ISO 80000-3 (Space and time)
  • Nautical mile definition (1 NM = 1852 m exactly)

Pressure & Force

  • BIPM SI Brochure (pascal, newton definitions)
  • NIST pressure unit standards
  • ISO 80000-4 (Mechanics)

Energy & Power

  • BIPM SI Brochure (joule, watt definitions)
  • ISO 80000-5 (Quantities and units — Thermodynamics)
  • NIST energy conversion factors

Area

  • BIPM SI Brochure (square meter definition)
  • NIST acre definition (exact conversion factors)
  • ISO 80000-3 (Space and time)

Time

  • BIPM SI Brochure (second definition)
  • ISO 80000-3 (Space and time)
  • Official calendar and astronomical time definitions

Data Storage

  • IEC 60027-2 (Binary prefixes: kibi, mebi, gibi, etc.)
  • ISO/IEC 80000-13 (Information technology)
  • IEEE 1541 (Prefixes for binary multiples)

Frequency

  • BIPM SI Brochure (hertz definition)
  • ISO 80000-3 (Space and time)
  • IEC standards for electrical frequency measurements

Fuel Consumption

  • ISO 80000-9 (Quantities and units — Physical chemistry and molecular physics)
  • EPA (US Environmental Protection Agency) standards
  • EU fuel consumption standards

Angle

  • BIPM SI Brochure (radian definition)
  • ISO 80000-3 (Space and time)
  • Mathematical and astronomical angle standards

Additional Reference Materials

  • SI Brochure (9th Edition, 2019): The official document defining the International System of Units. Available from BIPM
  • NIST Special Publication 330: The International System of Units (SI). Available from NIST
  • ISO 80000 Series: Quantities and Units standards covering all major measurement categories. Available from ISO
  • IEC 60027-2: Letter symbols to be used in electrical technology. Available from IEC
  • NIST Handbook 44: Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices. Available from NIST
  • Merriam-Webster Dictionary: Authoritative source for unit definitions and usage.

Verification Methodology

Every conversion factor on UnitsConverter.io is verified using the following process:

  1. Primary Source Research: We consult the official standards documents from BIPM, NIST, ISO, and IEC to obtain authoritative conversion factors.
  2. Cross-Verification: Each factor is checked against at least two independent sources to ensure consistency and accuracy.
  3. Mathematical Validation: All derived conversion factors are verified through mathematical calculation and tested with known values.
  4. Precision Testing: We verify that our implementation maintains the correct precision and handles edge cases appropriately.
  5. Documentation: Each page documents its sources and provides references for users who want to verify the information.

Questions About Sources?

If you have questions about any of our sources or want to verify specific information:

Contact us at sources@unitsconverter.io

We're happy to provide additional documentation or clarification about any conversion factor or unit definition.

Last Updated: February 20, 2026

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