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Guide

How to Convert Between Metric and Imperial Units

Learn how unit conversion works, the key conversion factors, and how to avoid common measurement mistakes.

Open the Unit Converter

A unit converter translates a measurement from one unit to another — metres to feet, kilograms to pounds, Celsius to Fahrenheit — using fixed conversion factors. It works for length, weight, volume, area, speed, and temperature.

How conversion works

Most conversions multiply by a factor: 1 metre = 3.28084 feet, so 5 metres = 5 × 3.28084 = 16.4 feet. Temperature is the exception because the Celsius and Fahrenheit scales have different zero points, so it uses a formula rather than a simple factor.

Key conversion factors

  • Length: 1 inch = 2.54 cm; 1 metre = 3.28084 ft; 1 mile = 1.60934 km.
  • Weight: 1 kg = 2.20462 lb; 1 ounce = 28.3495 g.
  • Volume: 1 litre = 0.264172 US gallon; 1 US gallon = 3.78541 L.
  • Temperature: °F = °C × 9/5 + 32; °C = (°F − 32) × 5/9.

How to use the converter

  1. Choose the measurement type (length, weight, etc.).
  2. Enter a value and select its unit.
  3. Select the target unit and read the converted value.

Examples

A 10 km run is 6.2137 miles. A 70 kg person weighs 154.3 lb. 20°C is 68°F — a comfortable room temperature. A 5 litre engine displaces about 1.32 US gallons.

When a unit converter is useful

  • Converting recipes between metric and imperial.
  • Understanding foreign measurements while travelling.
  • Checking product specs across regions.
  • Converting speeds, distances, or weights for work or study.

Common mistakes

Confusing US and UK gallons (1 UK gallon ≈ 4.546 L vs 1 US gallon ≈ 3.785 L) and mixing fluid ounces with weight ounces are the classic errors. Always confirm which system a figure uses before converting.

Put it into practice

Use the Unit Converter right now — free, in your browser, no sign-up required.

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