Formula
1 in = 2.54 cm (exact)1 ft = 12 in = 0.3048 m1 yd = 3 ft = 0.9144 m1 mi = 5,280 ft = 1.609344 km1 nmi = 1,852 m How it works
Since the 1959 international yard and pound agreement, the inch has been defined as exactly 2.54 centimeters. Every other US customary length follows from it, so conversions such as 1 foot = 0.3048 m and 1 mile = 1.609344 km are exact, not approximations.
The meter itself is defined by the speed of light: the distance light travels in a vacuum in 1/299,792,458 of a second. Metric prefixes then step by powers of ten — 1 km = 1,000 m, 1 m = 100 cm = 1,000 mm.
The nautical mile, used in aviation and shipping, is 1,852 m — roughly one minute of latitude. Choose any input unit and every other unit updates at once; heights are also shown in feet and inches.
Frequently asked questions
How many centimeters are in a foot?
Exactly 30.48 cm.
How do I convert my height from cm to feet and inches?
Switch the input unit to cm and enter your height; the “Feet and inches” output shows it directly. 175 cm is 5 ft 8.9 in.
Is a kilometer longer than a mile?
No. A mile is about 1.61 km, so 10 km (a “10K” race) is about 6.2 miles.