Units of Measurement List 📐

All Units of Measurement List 📐 SI, Imperial & USC Units 🗒️

Units of measurement as defined by metrology, the scientific study of measurement. ADDucation’s units of measurement list in order includes Metric SI units (International System of Units), Imperial units and United States Customary System (USCS). Where British, American, Canadian and Australian imperial units of volume differ we’ve included the differences.

• ADDucation’s list of all units of measurement was compiled by Joe Connor and last updated Dec 4, 2022 @ 3:39 pm

The 7 Base SI Units of Measurement Are Defined by Fundamental Constants

• Meter (m) length unit of measurement:
  Distance traveled by light in a vacuum in 1/299,792,458 seconds
• Second (s) time unit of measurement:
  9,192,631,770 cycles of radiation of an atom of caesium-133
• Kilogram (kg) mass unit of measurement:
  Planck’s constant divided by 6.626,070,15 × 10 −34 m −2 s
• Candela (cd) luminous intensity measurement unit:
  Light source with monochromatic radiation of frequency 540 × 10 12 Hz and radiant intensity of 1/683 watt per steradian
• Kelvin (K) temperature unit of measurement:
  Boltzmann constant, defined as a change in thermal energy of 1.380 649 × 10 −23 joules
• Ampere (A) electric current measurement unit:
  Flow equal to 1/1.602176634×10 −19 elementary charges per second
• Mole (mol) amount of substance measurement unit:
  Avogadro constant, defined as 6.02214076 ×10 23 elementary entities.

Base SI Units of Measurement Dependencies

• Metre is dependent on second because its length is defined in terms of the distance traveled by light in a fraction of a second
• Candela and Kelvin depend on the definition of energy, defined in terms of length (metre), mass (kilogram) and time (second)
• Ampere is dependent on time (second)
• Kilogram is defined in terms of time (second) and distance (metre).

Base SI Units & Dependencies (as redefined in 2019)
Created and released by ADDucation on CC0 1.0 terms.

Key: ≡ means “equivalent to” and ≈ means “approximately equal to” using a conversion factor. ADDucation Tips: Click arrows in column headings to sort measurement units. Reload page for original sort order. Resize your browser to full screen and/or zoom out to display as many columns as possible. Click the ➕ icon to reveal any hidden columns. Start typing in the Filter table box below to quickly find any imperial or metric units of measurement inside the table.

• Fundamental constant definition: In 1983 the meter was defined as the distance light travels in a vacuum in 1/299,792,458th of a second
• Historical definitions:
  • 1960, the metre was redefined in terms of a certain number of wavelengths of a specified transition in krypton-86.
  • 1799, 1 metre was defined by a prototype metre bar located in the French National Archives (the bar was replaced in 1889).
  • 1793: 1 metre was defined as one ten-millionth of the distance from the equator to the North Pole.

  One of 7 SI base units of measurement.

  • Twenty-five links make a rod
  • One hundred links make a chain
  • One thousand links make a furlong
  • Eight thousand links make a mile.
  • The international foot is a exactly 0.3048 meters
  • 🇺🇸 US Survey Foot is a fraction: 1200/3937 meters, a difference of one one-hundredth of a foot per mile
  • 🇬🇧 UK: 1 Imperial teaspoon ≈ 1.20095 US teaspoon ≈ 5.91939 ml
  • 🇺🇸 US: 1 US teaspoon ≡ 1 ⁄₃ US tablespoon ≡ 1 ⁄₆ US fluid ounce and ≈ 0.83 imperial teaspoon ≈ 4.93 ml
  • 🇬🇧 UK: 1 imperial tablespoon ≈ 1.20095 US tablespoon ≈ 17.7582 ml
  • 🇺🇸 US: 1 US tablespoon ≡ 3 US teaspoons ≡ 1 ⁄₂ US fluid ounce and ≈ 0.832674 imperial tablespoon ≈ 14.8 ml
  • 🇦🇺 Australia: 1 Australian tablespoon ≈ 20 ml
  • 🇨🇦 Canada: 1 Canadian tablespoon ≈ 15 ml
  • 🇬🇧 UK: 1 imperial fluid ounce ≈ 28.4130625 ml
    (1 imperial fluid ounce ≡ 1 ⁄₁₆₀ imperial gallon or 1 ⁄₂₀ imperial pint ≡ 1 ⁄₅ imperial gill ≈ 1.73 cubic inches ≈ 0.9588 US fluid ounces)
    To convert UK fluid ozs to ml multiply 28.4130625
    To convert ml to UK fluid ounces multiply by 0.03519507972 or divide by 28.4130625
    To convert imperial fluid ounces to US fluid ounces multiply by 0.9588 or divide by 1.043
  • 🇺🇸 US: 1 US fluid ounce ≈ 29.5735296 ml.
    (1 US fluid ounce ≡ 1 ⁄₁₂₈ US gallon ≡ 1 ⁄₁₆ US pint ≡ 1 ⁄₄ US gill ≡ 2 US tablespoons ≡ 6 US teaspoons and ≈ 1.04 imperial fluid ounces)
    To convert US fluid ozs to ml multiply 29.5735296
    To convert ml to US fluid ounces multiply by 0.033814 or divide by 29.5735296
    To convert US fluid ounces to UK fluid ounces multiply by 1.043 or divide by 0.9588.
  • 🇬🇧 UK: 1 cup ≡ 284.13 ml
  • 🇺🇸 USA: 1 cup ≡ 236.59 ml
  • 🇦🇺🇨🇦 Australia/Canada: ≡ 250 ml.
  • 🇬🇧 UK: 1 imperial gill ≡ 1 ⁄₄ imperial pint ≡ 5 imperial fluid ounces and ≈ 1.2 US gills ≈ 142 ml
  • 🇺🇸 US: 1 US liquid gill ≡ 1 ⁄₄ US liquid pint ≡ 4 US fluid ounces ≡ 1⁄32 US gallon and ≈ 5⁄6 imperial gills = 118 ml
  • 🇺🇸 US: 1 US dry gill = 138 ml.
  • 🇬🇧 UK: 1 imperial pint ≡ 1 ⁄₈ imperial gallon ≡ 4 imperial gills ≡ 20 imperial fluid ounces and ≈ 1.2 US liquid pints ≈ 568 ml
  • 🇺🇸 US: 1 US liquid pint ≡ 1 ⁄₈ US liquid gallon ≡ 16 US fluid ounces and ≈ 0.83 imperial pints ≈ 473 ml
  • 🇺🇸 US: 1 US dry pint ≡ 1 ⁄₈ US dry gallons ≡ 33.6 cubic inches and ≈ 0.97 imperial pints ≈ 551 ml.
  • 🇬🇧 UK: 1 imperial quart ≡ 1 ⁄₄ imperial gallon ≡ 40 imperial fluid ounces and ≈ 1.14 litres ≈ 38.43 US fluid ounces
  • 🇺🇸 US: 1 US liquid quart ≡ 1 ⁄₄ US liquid gallon ≡ 32 US fluid ounces and ≈ 33 imperial fluid ounces ≈ 946 ml
  • 🇺🇸 US: 1 US dry quart ≡ 1 ⁄₄ US dry gallon ≡ 67.2 cubic inches and ≈ 38.76 imperial fluid ounces ≈ 1101 ml.
  • 🇬🇧 UK: 1 imperial gallon was defined in 1824 as the volume of 10 pounds of water at 62°F and ≡ 8 imperial pints ≡ 160 imperial fluid ounces ≡ 4.55 liters and ≈ 1.2 US gallons
  • 🇺🇸 US: 1 US liquid gallon ≡ 8 US pints ≡ 16 US fluid ounces ≡ 3.78 liters and ≈ 0.83 imperial gallons
  • 🇺🇸 US: 1 US dry gallon ≡ 268.8 cubic inches ≈ 4.4 liters. Not used in commerce.
  • Fundamental constant definition (from World Metrology Day May 2019): Planck’s constant divided by 6.626,070,15 × 10 −34 m −2 s
  • International Prototype Kilogram (IPK aka Le Grande K and Big K): 1 kilogram = 1000g and is the mass of an international kilogram prototype, a cylinder made from a platinum-iridium alloy, which weighs ≈ 2.2 pounds.

  One of 7 SI base units of measurement. The kilogram is the only SI base unit with an SI prefix (see Grams).

  • 🇬🇧 UK: 8 stone or 112 lb (50.80234544 kg) long ton (2240 lb, 1016.0469088 kg) 2o hundredweights make a ton
  • 🇺🇸 US: 100 lb (45.359237 kg) short ton (2000 lb; 907.18474 kg) 2o hundredweights make a ton.
  • 🇬🇧 UK: 2240 lb ≡ 20 (UK) hundredweight ≈ 1016.047 kg (aka long ton, weight ton, gross ton, ton shortweight)
  • 🇺🇸 US (and formerly 🇨🇦 Canada): 2000 lb ≡ 20 (US) hundredweight ≈ 907.1847 kg (aka short ton, net ton).
  • 10 denier or less: ultra sheer
  • 10 to 30 denier: sheer
  • 30 to 40 denier: semi-opaque
  • 40 to 70 denier: opaque
  • 70 denier or more” thick opaque.
  • 3-5 mm Gauze (open weave, needlepoint canvases, facings, linings)
  • 4-6 mm Organza (bridal wear, evening wear, sheer curtains)
  • 5-16 mm Habutai (simple plain weave, used for linings, light clothing, lingerie etc.)
  • 6-8 mm Chiffon (translucent, lightweight, used for blouses, scarves, lingerie etc.)
  • 12-16 mm Crepe de Chine (crisp, crimpled silk, hundreds of weaves and variations)
  • 12-30 mm Charmeuse (weaved so the front has a sheen and the reverse is dull, tends to cling, used for drapes, bridal gowns, ties, linings etc.)
  • 35-40 mm Noil/Raw silk (rough texture, dull like cotton, often blended to make other materials. Silk over 30 mm is likely to be opaque).
  • Fundamental constant definition: The Boltzmann constant. Change in thermal energy of 1.380 649 × 10 −23 joules
  • Historical definition: One Kelvin is 1/273.16 of the thermodynamic temperature of the triple point of water (at which water vapor, ice and water co-exist in equilibrium) ≈0.0036609 °C.

  One of 7 SI base units of measurement.

  • 1 large calorie (Cal or kcal) is commonly used to indicate calories in food and by nutritionists. It’s roughly the amount of energy needed to increase the temperature of 1 kg of water by 1 °C
  • 1 small or gram calorie (cal) is roughly the amount of energy needed to increase the temperature of one gram of water by 1 °C.
  • Historical definition: One Candela = the light from one candle
  • Fundamental constant definition (taking into account the color of the light and its direction): Light source with monochromatic radiation of frequency 540 × 10 12 Hz (cycles per second in Hertz) and radiant intensity of 1/683 watt per steradian. The color is yellowish green, which the human eye distinguishes really well.

  One of 7 SI base units of measurement.

  • Historical definition: 1 ampere equates to a flow of one coulomb per second
  • Fundamental constant definition: Flow equal to 1/1.602 176 634×10 −19 elementary charges per second.

  One of 7 SI base units of measurement.

  • Fundamental constant definition: The number expressed by the Avogadro constant is defined as 6.022,140,76 ×10 23 elementary entities.

  One of 7 SI base units of measurement.

  See also: Fundamental Physical Constants…

  United States Customary System (USCS) Units of Measurement 🗒️

  US Customary System (USCS or USC)

  By 1893 most United States customary units were redefined using the metric system meter and kilogram units. The International System of Units (SI), preferred by the US National Institute of Standards and Technology (NIST), is used for most new units of measure or mixed with US customary units.

  Key Facts & Differences Between US & Imperial Units 🗒️

  Key Differences Between Imperial and USC Units

  • Length:
    Conversion between Imperial and USC Units of measurement for length is based on 1959 International Yard and Pound Agreement between the USA, Canada, the United Kingdom, Australia, New Zealand and South Africa which defines the international yard as exactly 0.9144 metres.
  • Volume:
    • Imperial and US Customary Units of measurement based on cubic length (cubic inch, cubic foot etc) are the SAME
    • Imperial and US Customary Units of measurement for specific volume units (bushel, gallon, fluid ounce etc) are DIFFERENT
    • USC units of measurement for volumes are DIFFERENT for fluids and dry goods:
    • Imperial units of measurement for specific volumes are the SAME for fluids and dry goods
    • Imperial and USC units of measurement for volumes EVEN WITH THE SAME NAMES are DIFFERENT specifically; teaspoon, tablespoon, cup fluid ounce, gill, pint, quart and gallon
    • USC units of measurement for DRY volumes (gallons, quarts, pints, gills) are approximately 3.3% smaller than the equivalent Imperial volume units of measurement
    • USC units of measurement for FLUID volumes (gallons, quarts, pints and gills are about 20% smaller than the equivalent Imperial volume units of measurement BUT Imperial fluid ounces are approximately 4% smaller than US fluid ounces
    • Canada uses a mixture of both systems which causes labeling confusion for units of measurement on bottles and cans.
    • Troy weight; for precious metals
    • Apothecaries’ weight; for medicines, now mostly superseded by metric units of measurement
    • Avoirdupois weight; most other purposes.
    Why Are Imperial & USC Units of Measurement Different? 🗒️

    Imperial & USCS Units of Measurement Are Different Because…

    In 1824 various different volume units of measurement, in use across the British Empire, were replaced with a single system based on the Imperial gallon. The US continued to use the “obsolete” Winchester measure and formally adopted it in 1836 to define the US dry gallon. The US fluid gallon was defined as 231 cubic inches. Both Imperial and USC units sub-divide a gallon into four quarts, eight pints and 32 gills.
    The US gill is divided into four US fluid ounces but the Imperial gill is divided into five Imperial fluid ounces. This leads to confusion when converting sub-divisions of fluid ounces.

    How Do Differences Between Imperial & US Units Affect YOU? 🙍

    How the Different Units of Measurement Affect YOU:

    • Body Weights: In the US body weight is measured in pounds, in the UK, and some other countries, body weight is still typically measured in stones and pounds (or kilograms)
    • Drivers: When comparing gas/petrol prices, or calculating miles per gallon (MPG), make sure you use the appropriate US Gallon to Imperial Gallons (or Litres) conversion
    • Cooks/Chefs: There’s a 4% difference between US and Imperial volume measurements (fluid ounces, cups, tablespoons, teaspoons) which isn’t usually an issue but be careful when translating US recipes into weights to take account of the content. For example 1 cup of flour weighs around 125 grams compared to a cup of Maple syrup at over 300 grams
    • Buying heavy items: UK and US tons (and hundredweights) are different and there’s also a metric tonne (metric ton). The difference between the heaviest (UK) and lightest (US) is 11%.

    Related ADDucation Lists:

    • List of Commonly Used Abbreviations (acronyms)…
    • Printable Periodic Table of Elements…
    • Units of measurement chart in German: Maßeinheiten & Formeln
    • Help improve ADDucation’s units of measurement list by adding your comments below…