Connects with SciGen Unit U1 Teacher Tune-up Quick Content Refresher for Busy Professionals

Units of measurements: an overview

Most of the world uses an organized system of units called SI, or Système international (d'unités), often called the metric system. The only countries that don’t are Myanmar, Liberia, and the USA. The “U.S. Customary” units commonly used in the USA (inches, miles, ounces, pounds, etc.) are slightly different from “Imperial” or “English” units, but people sometimes use those names anyway.

Because the metric system lends itself to clear calculation and communication, it is used by scientists even in the United States. At very large scales like distances to other stars and galaxies, astrophysicists (and sci-fi authors!) measure distance in light years or parsecs, which are not considered a part of either system.

Use this chart as a reference as you discuss different kinds of measurements with your students. You may also want to use this sortable chart in Google Sheets.

What’s being Metric System or SI U.S. customary units Miscellaneous measured (plus some archaic British units) linear distance / kilometer/kilometre (km) inch (sq. in.) football fields long length / width / meter/metre (m) foot (sq. ft.) block height centimeter/centimetre (cm) yard (sq. yd.) millimeter/millimetre (mm) mile (sq. mi.) parsec (pc) micron (μ) nautical mile light-year nanometer/nanometre (nm) mil, or thou (0.001 inch) astronomical unit (au) millimicron (mμ) chain angstrom (A) furlong rod cubit league

angle radian (rad) degree (°) gradian (grad) arcminute (arcmin) arcsecond (arcsec) area hectare (ha) square inch (sq. in.) football field square kilometer/kilometre (km2) square foot (sq. ft.) square meter/metre (m2) square yard (sq. yd.) square centimeter/ centimetre acre (ac) (cm2) square mile (sq. mi.)

Science Generation • serpmedia.org/scigen • © 2018 SERP Institute Page 1 of 3 capacity liter (L) gallon (gal) NOTE: Volume and milliliter (mL) quart (qt) capacity are especially pint (pt) easy to confuse. Volume cup (c) is the amount of three- tablespoon (Tb) dimensional space teaspoon (tsp) something occupies. The capacity, on the other 3 volume cubic meter/metre (m ) cubic inch (cu. in.) hand, describes how 3 cubic centimeter (cm ) cubic foot (cu. ft.) much of another cubic yard (cu. yd.) substance—a solid, a acre-foot liquid or a gas—an object dry pint can hold. The volume of a dry quart canoe would be peck unchanged if it were bushel flattened, but its capacity would be much diminished. In everyday use, “volume” is often used to mean capacity. To speak scientifically, however, it’s important to know the difference. mass / weight gram (g) grain kilogram (kg) ounce (oz) metric ton/tonne pound (lb) carat (ct) stone hundred-weight ton

density g/cm3 lb/ft3 pixels per inch (ppi) kg/m3 dots per inch (dpi) lines per inch (lpi) time second second fortnight minute minute lunar month hour hour dog year day day season year week month year decade century millennium

speed kilometers per hour (kph) miles per hour (mph) speed of light (c) meters per second miles per second knot force newton (N) pound weight (lbwt) dyne ton ounce-force pound-force

Science Generation • serpmedia.org/scigen • © 2018 SERP Institute Page 2 of 3 energy erg calorie (cal) barrels of oil newton-meter kilocalorie (kcal or Cal) tons of TNT joule (J) BTU (British thermal unit) watt-second therm watt-hour foot-pound kilowatt-hour (kWh) electron volt (ev) power watt horsepower kilowatt (KW) foot-pounds per second joules per second ft lbwt/sec ergs per second ft lbwt /min calories per second BTUs per hour decibel foot-pounds per second

pressure newtons per meter squared (N/m2) bar atmosphere dynes per cm2 pascal centimeters mercury lbwt/ft2 lbwt/in2 temperature degrees celsius (°C) degrees Fahrenheit (°F) Kelvin (K) [Note that the degree sign is not used with the Kelvin scale.]

frequency hertz (Hz) beats per minute frames per second revolutions per minute baud words per minute pages per minute electrical ampere or “amp” (A) — current circuits coulomb (C) — charge volt (V) — potential ohm (Ω) — resistance tesla (T) — magnetic field

luminosity candela (cd) lux lumen concentration Molarity (M) parts per million (ppm) parts per billion (ppb) karat (K or kt) proof

type height point (pt) pica (p) data Bit (B) byte word kilobyte (kB) megabyte (MB) gigabyte (GB) terabyte (TB)

Science Generation • serpmedia.org/scigen • © 2018 SERP Institute Page 3 of 3