An area of 43,560 square feet. Originally, the area a yoke of oxen could plow in one day.

Originally a measurement of type size (51/2 points). Now equal to 1/14 inch. Used in printing for measuring column length.

Unit of electric current. A potential difference of one volt across a resistance of one ohm produces a current of one ampere.

93,000,000 miles, the average distance of the earth from the sun. Used for astronomy.

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.

144 cubic inches (12 in. × 12 in. × 1 in.). Used for lumber.

40 yards. Used for measuring cloth.

British thermal unit. Amount of heat needed to increase the temperature of one pound of water by one degree Fahrenheit (252 calories).

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.

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.

18 inches or 45.72 cm. Derived from distance between elbow and tip of middle finger.

Unit of relative loudness. One decibel is the smallest amount of change detectable by the human ear.

11/4 yards or 1/32 bolt. Used for measuring cloth.

freight, ton (also called measurement ton)

40 cubic feet of merchandise. Used for cargo freight.

12 gross or 1728.

12 dozen or 144.

4 inches or 10.16 cm. Derived from the width of the hand. Used for measuring the height of horses at withers.

Modern unit for measurement of electromagnetic wave frequencies (equivalent to “cycles per second”).

2 liquid barrels or 14,653 cubic inches.

The power needed to lift 33,000 pounds a distance of one foot in one minute (about 11/2 times the power an average horse can exert). Used for measuring power of steam engines, etc.

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.

Not a distance, but the rate of speed of one nautical mile per hour. Used for measuring speed of ships.

Rather indefinite and varying measure, but usually estimated at 3 miles in English-speaking countries.

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.

Two-quart bottle. Used for measuring wine, etc.

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.

Approximately 3.26 light-years or 3.08 × 1013 km (1.92 × 1013 mi). Term is combination of first syllables of parallax and second, 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.

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.

1/6 inch or 12 points. Used in printing for measuring column width, etc.

2 hogsheads. Used for measuring wine and other liquids.

.013837 (approximately 1/72) inch or 1/12 pica. Used in printing for measuring type size.

100,000 grams or 220.46 pounds avoirdupois.

Used for measuring paper. Sometimes 24 sheets but more often 25. There are 20 quires to a ream.

Used for measuring paper. Sometimes 480 sheets, but more often 500 sheets.

International Unit of radiation exposure produced by X-rays.

20 units.

Usually placed at 1,088 ft. per second at 32°F at sea level. It varies at other temperatures and in different media.

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.

100 square feet. Used in building.

Legally 14 pounds avoirdupois in the U.K.

100,000 Btus.

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.

252 gallons, but often larger. Used for measuring wine and other liquids.

Unit of power. The power used by a current of one ampere across a potential difference of one volt equals one watt.