Metric vs Imperial: A Quick Conversion Guide
Most of the world uses metric; a few countries use imperial; and travellers, cooks and readers of international recipes constantly bounce between them. You do not need every factor — just a handful of everyday ones and a few mental shortcuts.
The conversions you actually use
- 1 inch = 2.54 cm; 1 foot = 30.5 cm; 1 mile = 1.609 km
- 1 kg = 2.205 lb; 1 lb = 454 g; 1 ounce = 28.35 g
- 1 litre = 1.057 US quarts; 1 US gallon = 3.785 L
- Temperature: F = C x 1.8 + 32
Mental shortcuts
You rarely need exact figures on the spot. Miles to kilometres: add about 60% (100 miles is roughly 160 km). Kilograms to pounds: just over double it. Centimetres to inches: divide by 2.5. Celsius to Fahrenheit: double and add 30. Each is a few percent off but close enough for everyday decisions.
The units that catch people out
A few traps recur. The US and imperial gallons and pints differ in size, so a "gallon" is ambiguous across countries. Weight uses "pounds" but scientists use mass; and a metric tonne (1,000 kg) is close to but not the same as an imperial ton. When precision matters — dosing, engineering, finance — convert with a tool rather than a shortcut.
Cooking conversions
Recipes are a common battleground. Cups are a volume measure that varies slightly by country, so for baking, weighing ingredients in grams is far more reliable than cups. Oven temperatures also differ: 350 F is about 175 C. The Length, Weight and Temperature converters here handle the exact numbers instantly.
Frequently asked questions
Which countries use imperial? Chiefly the United States for everyday measures, with the UK using a mix; most other countries are metric.
Is a US pint the same as a UK pint? No — the imperial pint is about 20% larger.
Why weigh instead of use cups? Because a cup of flour can vary a lot by how it is packed, while grams do not.
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Last updated: August 27, 2026