Measurement Terms

Units and conversion 7

• CentimeterA centimeter is a metric unit of length equal to one hundredth of a meter, about the width of a fingernail. Its symbol is cm. There are 100 centimeters in 1 meter and 10 millimeters in 1 centimeter, and 1 inch equals 2.54 centimeters.Grade 3, Grade 4, Grade 5
• Conversion FactorA conversion factor is a fraction whose top and bottom are the same amount written in different units, such as (12 in)/(1 ft), so it equals 1. Multiplying a measurement by it changes the units without changing the amount: 5 ft × (12 in)/(1 ft) = 60 in. Pick the version that cancels the unit you start with.Grade 6, Grade 7, Algebra 1
• Dimensional AnalysisDimensional analysis is a way to solve problems by tracking the units: you multiply by conversion factors, cancel any unit that appears on both the top and the bottom, and check that the units left over are the ones the answer needs. It is also called the factor-label method or unit analysis.Grade 7, Grade 8, Algebra 1
• KilometerA kilometer (km) is a metric unit of length equal to 1,000 meters, roughly six tenths of a mile. It measures long distances, such as the length of a road race or the distance between towns. To change kilometers to meters, multiply by 1,000: 3 km is 3,000 m.Grade 4, Grade 5, Grade 6
• MeterA meter (m) is a metric unit of length equal to 100 centimeters. It is the base unit of length in the metric system, a little over three feet (about 3.28 feet). A doorway is about 2 meters tall, and 1,000 meters make a kilometer. To change meters to centimeters, multiply by 100.Grade 3, Grade 4, Grade 5
• Metric SystemThe metric system is a system of measurement in which units are related by powers of 10. Its base units are the meter for length, the gram for mass and the liter for capacity. Prefixes name larger and smaller units: kilo- means 1,000, centi- means one hundredth and milli- means one thousandth, so 1 km = 1,000 m.Grade 4, Grade 5, Grade 6
• Unit ConversionUnit conversion is rewriting a measurement in a different unit without changing the amount, such as writing 3 feet as 36 inches. You multiply by a conversion factor, a fraction equal to 1 such as (12 in)/(1 ft). Converting to a smaller unit gives a larger number; converting to a larger unit gives a smaller number.Grade 4, Grade 5, Grade 6

Length and size 3

• HeightHeight is how tall something is: the distance from its bottom to its top, measured straight up and down. In geometry, the height of a shape is the perpendicular distance from a base to the opposite vertex or side, so it always meets the base at a right angle. Area and volume formulas use it.Grade 2, Grade 5, Grade 6
• LengthLength is how long something is: the distance from one end of an object to the other. You measure it by counting equal units laid end to end with no gaps or overlaps, such as inches, feet, centimeters or meters. A new pencil is about 7 inches long.Grade 1, Grade 2, Grade 3
• WidthWidth is the distance across a shape or object from side to side. In a rectangle, width is one of the two side measurements used with length, usually the shorter one, and multiplying length by width gives the area of a rectangle. Width is measured in length units such as inches, feet, centimeters or meters.Grade 3, Grade 4, Grade 5

Customary units 4

• FootA foot is a US customary unit of length equal to 12 inches, about the length of a standard school ruler. Its abbreviation is ft, and its plural is feet. There are 3 feet in a yard and 5,280 feet in a mile, and 1 foot is exactly 30.48 centimeters.Grade 2, Grade 3, Grade 4
• InchAn inch is a US customary unit of length equal to one twelfth of a foot, about the width of an adult thumb. Its abbreviation is in. Rulers split each inch into halves, quarters, eighths and sixteenths. One inch is exactly 2.54 centimeters, and 12 inches make 1 foot.Grade 2, Grade 3, Grade 4
• MileA mile (mi) is a US customary unit of length for long distances, equal to 5,280 feet or 1,760 yards. One mile is about 1.61 kilometers, so it is longer than a kilometer. Road distances and speed limits in the United States use miles and miles per hour.Grade 4, Grade 5, Grade 6
• YardA yard (yd) is a US customary unit of length equal to 3 feet or 36 inches. It is a little shorter than a meter: 1 yard is exactly 0.9144 meter. Yards measure fabric, rooms, gardens and the length of a football field, which is 100 yards between the goal lines.Grade 2, Grade 3, Grade 4

Time and temperature 1

• Elapsed TimeElapsed time is the amount of time that passes between a start time and an end time. To find it, count forward from the start in easy jumps (to the next hour, then whole hours, then the leftover minutes) and add the jumps. From 9:40 to 11:15, the elapsed time is 1 hour 35 minutes.Grade 3, Grade 4, Grade 5

Mass, weight and capacity 2

• GramA gram is a metric unit of mass, about the mass of a paper clip. Its symbol is g. There are 1,000 grams in a kilogram and 1,000 milligrams in a gram. Grams measure light things, such as food portions, coins and letters; heavier things are measured in kilograms.Grade 3, Grade 4, Grade 5
• KilogramA kilogram is the base unit of mass in the metric system (SI), equal to 1,000 grams. Its symbol is kg. A liter of water has a mass of about 1 kilogram, and 1 kilogram is about 2.2 pounds. Kilograms measure heavier things, such as people, bags of flour or luggage.Grade 3, Grade 4, Grade 5

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Updated November 2026·Reviewed by the Effortless Math team