According to the International System of Units (SI), the basic unit of metric length is a meter (m). That means distance in SI is measured in meters. To calculate larger or smaller values, units derived from metric units are used.

1 km is 1,000 m.
1 m is 100 cm.
1 cm is 10 mm.

In some countries, length is measured in inches (in), feet (ft), yards (yd), and miles (mi). A foot is a unit of measurement equal to the length of a human foot. One foot is equal to 30.48 cm. Smaller lengths are measured in inches: 1 inch is equal to 1/12 of a foot, or 2.54 cm. Miles measure longer lengths, and yards measure medium lengths.

1 mile is equal to 5,280 feet, 1,760 yards, or 1.609 km.
1 yard equals 3 feet, 36 inches, or 0.9144 meters.
1 foot equals 12 inches or 0.3048 meters.
1 m is approximately 39.37 inches.

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