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education 2025-02-06

Metric vs Imperial: The Complete Conversion Guide

Everything you need to know about metric and imperial systems, key conversions, and which countries use what.

Only three countries have not officially adopted the metric system: the United States, Myanmar, and Liberia.

Quick Reference Conversions

Length

MetricImperialQuick Estimate

|--------|----------|---------------|

1 cm0.394 in~2/5 inch 1 m3.281 ft~3 ft 3 in 1 km0.621 mi~5/8 mile

Weight

MetricImperialQuick Estimate

|--------|----------|---------------|

1 g0.035 oza paperclip 1 kg2.205 lb~2.2 lbs 100 kg220.5 lb~220 lbs

Temperature

  • 0°C = 32°F (water freezes)
  • 20°C = 68°F (room temperature)
  • 37°C = 98.6°F (body temperature)
  • 100°C = 212°F (water boils)

Volume

MetricImperialQuick Estimate

|--------|----------|---------------|

1 mL0.034 fl oz~20 drops 1 L0.264 gal~1 quart 3.785 L1 gallon~4 liters

Memory Tricks

  • A meter is roughly one large step
  • A kilogram is about 2 bags of sugar stacked (in US 1-lb bags)
  • A liter is slightly more than a quart
  • 30°C is hot summer weather; 0°C is freezing
  • For km to miles: multiply by 0.6 (or use Fibonacci: 5 km ≈ 3 mi, 8 km ≈ 5 mi)

Why the Metric System Is Simpler

Everything is base-10:

  • 10 mm = 1 cm
  • 100 cm = 1 m
  • 1000 m = 1 km

Compare with imperial:

  • 12 inches = 1 foot
  • 3 feet = 1 yard
  • 5,280 feet = 1 mile

Use our [Unit Converter](/en/unit-converter) for instant conversions.