# Miscellaneous Units of Measure

Below is information about units of measure, including acre, bolt, gross, hertz, knot, light-year, parsec, pi, ream, sound, square, stone, and more.

- acre
- An area of 43,560 square feet. Originally, the area a yoke of oxen could plow in one day.
- agate
- Originally a measurement of type size (5
^{1}/2 points). Now equal to^{1}/14 inch. Used in printing for measuring column length. - ampere
- Unit of electric current. A potential difference of one volt across a resistance of one ohm produces a current of one ampere.
- astronomical unit (A.U.)
- 93,000,000 miles, the average distance of the earth from the sun. Used for astronomy.
- bale
- A large bundle of goods. In the U.S., the approximate weight of a bale of cotton is 500 pounds. The weight varies in other countries.
- board foot (fbm)
- 144 cubic inches (12 in. × 12 in. × 1 in.). Used for lumber.
- bolt
- 40 yards. Used for measuring cloth.
- Btu
- British thermal unit. Amount of heat needed to increase the temperature of one pound of water by one degree Fahrenheit (252 calories).
- carat (c)
- 200 milligrams or 3.086 grains troy. Originally the weight of a seed of the carob tree in the Mediterranean region. Used for weighing precious stones.
- chain (ch)
- A chain 66 feet or one-tenth of a furlong in length, divided into 100 parts called links. One mile is equal to 80 chains. Used in surveying and sometimes called Gunter's or Surveyor's chain.
- cubit
- 18 inches or 45.72 cm. Derived from distance between elbow and tip of middle finger.
- decibel
- Unit of relative loudness. One decibel is the smallest amount of change detectable by the human ear.
- ell, English
- 1
^{1}/4 yards or^{1}/32 bolt. Used for measuring cloth. - freight, ton (also called measurement ton)
- 40 cubic feet of merchandise. Used for cargo freight.
- great gross
- 12 gross or 1728.
- gross
- 12 dozen or 144.
- hand
- 4 inches or 10.16 cm. Derived from the width of the hand. Used for measuring the height of horses at withers.
- hertz
- Modern unit for measurement of electromagnetic wave frequencies (equivalent to “cycles per second”).
- hogshead (hhd)
- 2 liquid barrels or 14,653 cubic inches.
- horsepower
- The power needed to lift 33,000 pounds a distance of one foot in one minute (about 1
^{1}/2 times the power an average horse can exert). Used for measuring power of steam engines, etc. - karat (kt)
- A measure of the purity of gold, indicating how many parts out of 24 are pure. For example: 18-karat gold is
^{3}/4 pure. Sometimes spelled*carat.* - knot
- Not a distance, but the rate of speed of one nautical mile per hour. Used for measuring speed of ships.
- league
- Rather indefinite and varying measure, but usually estimated at 3 miles in English-speaking countries.
- light-year
- 5,880,000,000,000 miles, the distance light travels in a vacuum in a year at the rate of 186,281.7 miles (299,792 kilometers) per second. (If an astronomical unit were represented by one inch, a light-year would be represented by about one mile.) Used for measurements in interstellar space.
- magnum
- Two-quart bottle. Used for measuring wine, etc.
- ohm
- Unit of electrical resistance. A circuit in which a potential difference of one volt produces a current of one ampere has a resistance of one ohm.
- parsec
- Approximately 3.26 light-years or 3.08 × 10
^{13}km (1.92 × 10^{13}mi). Term is combination of first syllables of*par*allax and*sec*ond, and distance is that of imaginary star when lines drawn from it to both Earth and the Sun form a maximum angle or parallax of one second (^{1}/3600 degree). Used for measuring interstellar distances. - pi (π)
- 3.14159265+. The ratio of the circumference of a circle to its diameter. For practical purposes, the value is used to four decimal places: 3.1416.
- pica
^{1}/6 inch or 12 points. Used in printing for measuring column width, etc.- pipe
- 2 hogsheads. Used for measuring wine and other liquids.
- point
- .013837 (approximately
^{1}/72) inch or^{1}/12 pica. Used in printing for measuring type size. - quintal
- 100,000 grams or 220.46 pounds avoirdupois.
- quire
- Used for measuring paper. Sometimes 24 sheets but more often 25. There are 20 quires to a ream.
- ream
- Used for measuring paper. Sometimes 480 sheets, but more often 500 sheets.
- roentgen
- International Unit of radiation exposure produced by X-rays.
- score
- 20 units.
- sound, speed of
- Usually placed at 1,088 ft. per second at 32°F at sea level. It varies at other temperatures and in different media.
- span
- 9 inches or 22.86 cm. Derived from the distance between the end of the thumb and the end of the little finger when both are outstretched.
- square
- 100 square feet. Used in building.
- stone
- Legally 14 pounds avoirdupois in the U.K.
- therm
- 100,000 Btus.
- township
- U.S. land measurement of almost 36 square miles. The south border is 6 miles long. The east and west borders, also 6 miles long, follow the meridians, making the north border slightly less than 6 miles long. Used in surveying.
- tun
- 252 gallons, but often larger. Used for measuring wine and other liquids.
- watt
- Unit of power. The power used by a current of one ampere across a potential difference of one volt equals one watt.