Metric to Imperial: The Conversions Worth Memorizing

You don't need a full conversion table in your head. A few exact factors, plus a shortcut for each, cover most everyday situations.

Length

• 1 inch = 2.54 cm exactly (this is how the inch is defined).
• 1 foot = 30.48 cm; 1 meter ≈ 3.28 feet.
• 1 mile = 1.609344 km exactly; 1 km ≈ 0.621 miles.

Shortcut: to turn kilometers into miles, multiply by 6 and divide by 10, so 10 km ≈ 6 miles. Neighboring Fibonacci numbers also work: 5 miles ≈ 8 km and 8 miles ≈ 13 km.

Weight

• 1 kilogram ≈ 2.2046 pounds.
• 1 pound = 0.45359237 kg exactly.
• 1 ounce ≈ 28.35 g.

Shortcut: double the kilograms and add 10%. 70 kg → 140 + 14 = 154 lb (exactly 154.3).

Temperature

Temperature uses a formula rather than a single factor, because the two scales start from different zero points:

Shortcut from °C to °F: double it and add 30. 20 °C → about 70 °F (exactly 68 °F). The shortcut drifts at extremes, so use the formula for cooking and medicine.

Handy anchors: 0 °C = 32 °F (water freezes), 37 °C = 98.6 °F (typical body temperature) and 100 °C = 212 °F (water boils at sea level).

Volume

• 1 US gallon ≈ 3.785 liters; 1 UK (imperial) gallon ≈ 4.546 liters.
• 1 US fluid ounce ≈ 29.57 ml.
• 1 liter ≈ 1.057 US quarts.

Watch out: US and UK gallons, pints and fluid ounces are different sizes. A British pint (568 ml) is larger than an American one (473 ml).

Area

• 1 square meter ≈ 10.764 square feet.
• 1 hectare = 10,000 m² ≈ 2.471 acres.

Area factors are squared: 1 m ≈ 3.28 ft, so 1 m² ≈ 3.28 × 3.28 ≈ 10.76 ft².