| From | To | Multiply by | Example |
|---|---|---|---|
| Inches (in) | Centimeters (cm) | 2.54 | 12 in = 30.48 cm |
| Centimeters (cm) | Inches (in) | 0.3937 | 30 cm = 11.81 in |
| Feet (ft) | Meters (m) | 0.3048 | 6 ft = 1.83 m |
| Meters (m) | Feet (ft) | 3.28084 | 5 m = 16.40 ft |
| Miles (mi) | Kilometers (km) | 1.60934 | 10 mi = 16.09 km |
| Kilometers (km) | Miles (mi) | 0.62137 | 100 km = 62.14 mi |
| Yards (yd) | Meters (m) | 0.9144 | 100 yd = 91.44 m |
| Nautical Miles (nmi) | Kilometers (km) | 1.852 | 1 nmi = 1.852 km |
Length Conversion Guide — Metric, Imperial & Real-World Reference
Length is the most fundamental measurement in everyday life — from shoe sizes to room dimensions, running distances to road signs. The world uses two primary systems: the metric system (used by 95% of the world) and the imperial/US customary system.
Metric System — Base Unit: Meter (m)
1 kilometer (km) = 1,000 m | 1 meter = 100 cm | 1 cm = 10 mm | 1 mm = 1,000 µm. The meter is defined as the distance light travels in 1/299,792,458 of a second — the most precise measurement standard ever created.
Imperial / US Customary
1 mile = 1,760 yards = 5,280 feet = 63,360 inches. 1 foot = 12 inches. 1 yard = 3 feet. The foot was historically the length of a human foot — standardized to 0.3048 m in 1959.
Real-World References
Average door height: 2.03 m (6 ft 8 in) | Football field: 91.44 m (100 yd) | Marathon: 42.195 km (26.22 mi) | Eiffel Tower: 330 m | Mount Everest: 8,849 m | Earth circumference: 40,075 km
Nautical Miles
1 nautical mile = 1.852 km = 1.151 miles. Originally defined as 1 minute of arc along a meridian, nautical miles are used in aviation and maritime navigation because they correspond directly to degrees of latitude.