Metric & US Conversion Cheat Sheet

Only three countries officially use the imperial/US customary system as their primary measurement system: the United States, Liberia, and Myanmar. The UK uses a mix — metric officially, but miles for road signs, pints for beer, and stones for body weight remain culturally embedded. Canada uses metric but informally many Canadians still reference feet/inches and Fahrenheit due to proximity to the US.

Double the Celsius temperature, subtract 10%, then add 32. Example: 25°C → 25×2=50 → 50−5=45 → 45+32=77°F (actual: 77°F ✓). For Fahrenheit to Celsius: subtract 32, then halve and add 10%. These shortcuts work well for everyday temperatures. The exact formula is °F = (°C × 9/5) + 32.

The US customary system and the British imperial system diverged after American independence. A US pint = 473ml (16 fl oz). A British imperial pint = 568ml (20 fl oz). This affects ordering beer in pubs — a UK 'pint' is larger. Australia, Canada, and most Commonwealth countries use metric but some informally refer to the UK pint.

In everyday use, 'weight' means mass. Scientifically, mass is measured in kg/g and is constant regardless of gravity. Weight is a force (measured in Newtons) = mass × gravitational acceleration. On the Moon, your mass is the same but your weight (force) is 1/6 of Earth's. Scales on Earth measure mass in kg because the relationship between force and mass is constant at Earth's surface gravity (9.81 m/s²).