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Common Unit Conversions — The Quick Reference Guide

The most searched conversions for length, weight, temperature, volume and area — with shortcuts.

📖 5 min read  ·  Updated May 2025  ·  ConvertersEveryday

These are the unit conversions people search for most often. Bookmark this page or use the conversion shortcuts for quick mental estimates.

Length

  • 1 km = 0.621 miles (rough: multiply km by 0.6, or multiply by 5 and divide by 8)
  • 1 mile = 1.609 km (rough: multiply miles by 1.6)
  • 1 metre = 3.281 feet = 39.37 inches
  • 1 cm = 0.394 inches (rough: divide cm by 2.54)
  • 1 inch = 2.54 cm
  • 1 foot = 30.48 cm

Weight / Mass

  • 1 kg = 2.205 lbs (rough: multiply kg by 2.2)
  • 1 lb = 0.454 kg
  • 1 stone = 14 lbs = 6.35 kg
  • 1 tonne (metric) = 1,000 kg = 2,205 lbs

Temperature

  • °C to °F: multiply by 9/5 then add 32. Or: double it and add 30 (rough estimate)
  • °F to °C: subtract 32 then multiply by 5/9
  • Key: 0°C=32°F, 20°C=68°F, 37°C=98.6°F, 100°C=212°F

Volume

  • 1 litre = 0.264 US gallons = 0.220 UK gallons
  • 1 US gallon = 3.785 litres
  • 1 UK gallon = 4.546 litres (20% larger than US gallon)
  • 1 cup (US) = 236.6 ml
  • 1 fl oz (US) = 29.57 ml; 1 fl oz (UK) = 28.41 ml

Area

  • 1 m² = 10.764 ft²
  • 1 hectare = 10,000 m² = 2.471 acres
  • 1 acre = 4,047 m² = 0.405 hectares

Speed

  • 1 km/h = 0.621 mph
  • 1 mph = 1.609 km/h
  • 1 knot = 1.852 km/h = 1.151 mph

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Frequently Asked Questions

How do I convert km to miles?
Multiply km by 0.621371. Quick estimate: multiply by 0.6 (slightly under). 10 km = 6.21 miles. 100 km = 62.1 miles. To reverse: multiply miles by 1.60934.
How do I convert kg to lbs?
Multiply kg by 2.20462. Quick estimate: multiply by 2.2. 70 kg = 154.3 lbs. To reverse: divide lbs by 2.20462 or multiply by 0.4536.
How do I convert Celsius to Fahrenheit?
°F = (°C × 9/5) + 32. Quick estimate: double °C and add 30 (gives ±2°F accuracy). Key reference: 0°C=32°F (freezing), 20°C=68°F (room temp), 37°C=98.6°F (body), 100°C=212°F (boiling).
What is the difference between a UK and US gallon?
A US gallon = 3.785 litres. A UK/Imperial gallon = 4.546 litres — about 20% larger. When comparing fuel economy (mpg), UK mpg figures appear about 20% higher than US mpg for the same vehicle because the UK gallon is bigger.
How do I convert square metres to square feet?
Multiply m² by 10.764. So 100 m² × 10.764 = 1,076.4 sq ft. To reverse: multiply sq ft by 0.0929.