Unit converter

Instantly convert between metric and imperial units across four categories. Results update as you type.

Length: km, miles, feet, inches & more
Weight: kg, lbs, stone, oz & more
Temperature: °C, °F, Kelvin
Volume: litres, gallons, pints & more

Metric vs imperial: a quick guide

The metric system (SI) is used by almost every country for science, medicine, and trade. The United Kingdom uses a mix — metric for most purposes, but miles on road signs, pints in pubs, and stone for body weight in everyday speech. The United States remains one of the few countries that has not fully adopted metric.

When calculating your BMI, you will need your weight in kg and height in metres or centimetres — use this converter first, then head to our BMI calculator.

Common conversions at a glance

Length	Equivalent
1 inch	2.54 cm
1 foot	30.48 cm
1 mile	1.609 km
1 kilometre	0.621 miles

Weight	Equivalent
1 kg	2.205 lbs
1 stone	6.350 kg / 14 lbs
1 lb	453.6 g

Temperature	Formula
°C to °F	(°C × 9/5) + 32
°F to °C	(°F − 32) × 5/9
°C to Kelvin	°C + 273.15

Volume	Equivalent
1 litre	1.760 pints (UK)
1 UK gallon	4.546 litres
1 US gallon	3.785 litres

Frequently asked questions

How many miles in a kilometre?

One kilometre equals approximately 0.621 miles. One mile equals approximately 1.609 kilometres. A useful rough rule: multiply km by 0.6 for a quick miles estimate.

How do I convert Celsius to Fahrenheit?

Multiply the Celsius value by 9/5 (or 1.8), then add 32. For example, 20°C = (20 × 1.8) + 32 = 68°F.

What is 100°F in Celsius?

100°F is approximately 37.78°C — just above normal human body temperature of 37°C. A body temperature of 100°F or more is considered a fever.

How many kg in a stone?

One stone equals 6.35029 kg, or exactly 14 pounds. So 10 stone = 63.5 kg; 12 stone = 76.2 kg.

Why does the UK use both metric and imperial?

The UK officially adopted the metric system in the 1960s and 70s, but some imperial units proved too culturally embedded to replace — miles on roads, pints in pubs, and stone for weight have all persisted alongside metric. The law allows both in many contexts.

What is the difference between a UK pint and a US pint?

A UK (imperial) pint is 568 ml; a US pint is 473 ml. The same difference applies to gallons — a UK gallon is 4.546 litres vs 3.785 litres for a US gallon. Always check which system is being used in recipes and fuel comparisons.

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