Guide · Updated November 2026 · How we check our numbers
Metric vs Imperial: The Exact Conversion Factors to Know
Since the 1959 international yard and pound agreement, US and imperial units are defined exactly in metric terms. That makes conversions precise.
Length
- 1 inch = 2.54 cm exactly
- 1 foot = 0.3048 m · 1 yard = 0.9144 m
- 1 mile = 1.609344 km
Shortcut: to turn km into miles, multiply by 0.6 for a quick estimate (10 km ≈ 6.2 miles).
Weight
1 pound = 0.45359237 kg exactly, and 1 kg ≈ 2.2046 lb. So 150 lb ≈ 68.04 kg.
Volume: two different gallons
A US gallon is 3.785 L, but a UK (imperial) gallon is 4.546 L — about 20% bigger. That is why UK mpg figures look higher than US ones for the same car.
Temperature
°F = °C × 9/5 + 32 and °C = (°F − 32) × 5/9. Body temperature 98.6 °F is 37 °C. The scales meet at −40°.
Area
1 acre = 43,560 ft² ≈ 4,047 m², and 1 hectare ≈ 2.471 acres.
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This guide is general information, not professional advice.