Converting Units
Grade 5 · Math · Study Guide
Learn to convert between units in the U.S. customary and metric measurement systems.
Converting units means changing a measurement from one unit to another of the same type (e.g., feet to inches). To convert to a smaller unit, multiply. To convert to a larger unit, divide.
The U.S. customary system uses units like inches, feet, yards, miles, ounces, pounds, cups, pints, quarts, and gallons. Memorizing key conversion facts (like 12 inches = 1 foot) lets you set up multiplication or division to convert.
The metric system is based on powers of 10, which makes converting easier. Common prefixes tell you the relationship: kilo- (1,000), centi- (1/100), milli- (1/1,000).
| From | To | Multiply By |
|---|---|---|
| feet | inches | 12 |
| yards | feet | 3 |
| pounds | ounces | 16 |
| gallons | quarts | 4 |
| quarts | pints | 2 |
| pints | cups | 2 |
| From | To | Multiply By |
|---|---|---|
| kilometers | meters | 1,000 |
| meters | centimeters | 100 |
| kilograms | grams | 1,000 |
| liters | milliliters | 1,000 |
Key terms
- Conversion Factor
- The number used to multiply or divide when changing between units (e.g., 12 for inches to feet).
- Customary Units
- The U.S. measurement system using inches, feet, pounds, gallons, etc.
- Metric Units
- An international measurement system based on powers of 10 using meters, liters, and grams.
- Benchmark
- A familiar measurement used to estimate others (e.g., a doorknob is about 1 meter high).
Practice questions
How many inches are in 4 feet?
- 16
- 36
- 48
- 52
Show answer
Answer: 48
1 foot = 12 inches. 4 × 12 = 48 inches.
How many meters are in 3 kilometers?
- 300
- 3,000
- 30
- 30,000
Show answer
Answer: 3,000
1 km = 1,000 m. 3 × 1,000 = 3,000 m.
72 inches = ___ feet
Show answer
Answer: 6
Divide by 12: 72 ÷ 12 = 6 feet.
2 gallons = ___ quarts
Show answer
Answer: 8
1 gallon = 4 quarts. 2 × 4 = 8 quarts.
Which is larger: 1.5 kg or 1,200 g?
- 1.5 kg
- 1,200 g
- They are equal
- Cannot compare
Show answer
Answer: 1.5 kg
1.5 kg = 1,500 g. 1,500 g > 1,200 g, so 1.5 kg is larger.
Fun facts
- Only three countries do not officially use the metric system: the United States, Liberia, and Myanmar.
- The metric system was invented during the French Revolution so scientists everywhere could share measurements easily.
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