History & Background
The metric system was adopted by the French National Assembly in 1795, defining the meter as one ten-millionth of the distance from the equator to the North Pole. The 1959 international yard and pound agreement standardised the foot at exactly 0.3048 m and the mile at exactly 1,609.344 m, making metric–imperial conversions exact rather than approximate.
Conversion Formulas
1 meter = 3.28084 feet = 39.3701 inches1 kilometer = 0.621371 miles1 mile = 1.609344 kilometers (exact)1 inch = 2.54 cm (exact, by 1959 agreement)1 yard = 0.9144 m (exact)
Common Values
- 1 m = 100 cm = 1,000 mm
- 1 km = 1,000 m = 0.6214 mi
- 5 km ≈ 3.107 mi (a 5K race)
- 1 mi = 1,760 yd = 5,280 ft
- 6 ft ≈ 1.83 m (average male height)
- 1 inch = 25.4 mm
Common Uses
- Travel and navigation between metric and imperial countries
- DIY and construction (matching US lumber to European measurements)
- Shipping and parcel dimensions
- Sports — race distances, height, jump distances
- Engineering drawings and machining tolerances
Practical Tips
- For everyday estimation: 1 meter ≈ 3.28 ft, 1 inch ≈ 2.5 cm.
- Aviation and maritime industries still use feet (altitude) and nautical miles.
- Wood thickness in the US is sold in nominal inches that are smaller than actual.
Frequently Asked Questions
How many feet are in a meter?
Exactly 3.28084 feet. A 1.8 m doorway is about 5 ft 11 in.
How many kilometers in a mile?
1 mile = 1.609344 km exactly. So 60 mph ≈ 96.56 km/h.
Is 1 inch exactly 2.54 cm?
Yes — defined exactly by the 1959 international yard and pound agreement.
Why are some countries still using feet and inches?
The US, Liberia and Myanmar still use US customary units; the UK uses a mix (miles for road distance, meters for everything else).
How long is a marathon in miles?
42.195 km = 26.2188 miles. The official "marathon distance" is 26 miles 385 yards.