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The Unit Conversion Cheat Sheet: 40 Conversions Worth Memorizing

Updated: July 2026

You do not need to memorize every conversion factor — a handful covers almost everything daily life throws at you. Here is our curated cheat sheet, organized so the numbers stick.

Length

  • 1 inch = 2.54 cm (exact)
  • 1 foot = 30.48 cm
  • 1 yard ≈ 0.91 m (a yard is a short meter)
  • 1 mile = 1.609 km
  • 1 nautical mile = 1.852 km

Weight

  • 1 ounce = 28.3 g
  • 1 pound = 454 g (a pound is a light half-kilo)
  • 1 stone = 6.35 kg
  • 1 US ton = 907 kg; 1 metric tonne = 1,000 kg

Volume

  • 1 teaspoon = 5 ml; 1 tablespoon = 15 ml
  • 1 US cup = 237 ml
  • 1 US pint = 473 ml (a UK pint is 568 ml)
  • 1 US gallon = 3.79 L (a UK gallon is 4.55 L)

Temperature anchors

Instead of formulas, memorize anchor points: 0°C = 32°F (freezing), 10°C = 50°F (cool), 20°C = 68°F (room), 30°C = 86°F (hot day), 37°C = 98.6°F (body), 100°C = 212°F (boiling). Between anchors, every 5°C step is 9°F.

The universal shortcuts

km to miles: multiply by 0.6. kg to pounds: double it and add 10%. Liters to US gallons: divide by 4 (roughly). cm to inches: divide by 2.5. These four shortcuts, accurate within a few percent, handle most travel and shopping situations without a calculator.

Related converters

Frequently asked questions

What is the easiest way to convert kg to pounds in your head?

Double the kilograms and add 10% of the result. 70 kg → 140 + 14 = 154 lbs, which is exact to within a fraction of a percent.

Which conversions are exact rather than approximate?

Inch-centimeter (2.54 exactly), pound-kilogram (0.45359237 exactly) and most metric-imperial pairs are exact by international definition since 1959. Rounded figures like "1 mile ≈ 1.6 km" are conveniences.

How accurate are mental shortcuts?

The shortcuts here stay within about 3% — fine for travel, cooking and shopping. For engineering, medicine or anything structural, use full-precision factors instead.