Height Converter
Weight Converter
These Conversions Are Exact
Unlike shoe sizes or cup measures, height and weight conversions have no ambiguity in them. An inch has been defined as exactly 25.4 millimetres since the international yard and pound agreement of 1959, and a pound as exactly 0.45359237 kilograms. Those are definitions, not measurements, so the numbers above are as precise as the figures you type in.
The only rounding happens in the display. Enter 5 feet 9 inches and you get 175.26 cm, which is exact rather than approximate.
Stone, and Why It Confuses Everyone
Britain and Ireland measure body weight in stone and pounds, where one stone is 14 pounds. Someone who weighs 150 pounds is 10 stone 10, written 10st 10lb and said aloud as “ten stone ten”.
Two things trip people up. The remainder is always given in pounds, never as a decimal, so 10.7 stone is not a thing anyone says. And the unit is almost exclusively used for people: nobody weighs luggage or flour in stone.
The US uses plain pounds for body weight and does not use stone at all, which is why an American reading a British forum post about losing “a stone” is reading about 6.35 kg.
Handy Reference Points
Worth memorising if you switch between systems often:
- 6 feet is 182.9 cm, near enough 183
- 5 feet 10 inches is 177.8 cm
- 5 feet 6 inches is 167.6 cm
- 180 cm is 5 feet 10.9 inches, so just under 5 feet 11
- 1 kg is 2.205 lb, so doubling and adding 10 percent gets you close in your head
- 100 kg is 220.5 lb, or 15 stone 10
- 1 stone is 6.35 kg
The mental shortcut for kilograms to pounds is to double and add ten percent: 70 kg gives 140 plus 14, or 154, against a true 154.3. Close enough for conversation.
Frequently Asked Questions
Who Still Uses Which System
Three countries have not adopted the metric system for everyday use: the United States, Liberia and Myanmar. Everywhere else officially uses metric, but official and everyday are not the same thing.
The United Kingdom is the clearest example. Road signs are in miles, beer is in pints, babies are announced in pounds and ounces, and body weight is in stone. Meanwhile school science is metric, food packaging is in grams, and a doctor will record your height in centimetres. Most British people can state their own height in feet and inches and would struggle to say it in centimetres without working it out.
Canada is metric on paper and mixed in practice. Height and body weight are commonly given in feet, inches and pounds, while temperature, distance and groceries are metric. Australia and New Zealand went metric decisively in the 1970s and use centimetres and kilograms with little ambiguity.
This matters when reading anything international. A height given as 175 without units is centimetres. A weight given as 12 stone is British. A weight given as 165 with no unit, on an American site, is pounds.
Rounding, and When It Matters
The converter shows height to one decimal place and weight to two, which is more precision than most situations need and less than the underlying arithmetic holds.
For a form asking your height, round to the nearest centimetre or half inch. Nobody needs 175.26. For shipping and freight, round up rather than down, because carriers charge on the bracket above. For anything medical, use whatever precision the form asks for and do not convert twice: converting pounds to kilograms and back introduces rounding error each way, so keep the original figure and convert once.
That last point catches people out with recipe scaling and dosing. Each conversion step rounds, and rounding compounds. Convert from the source number every time rather than from your previous answer.
Related Tools
For kitchen quantities rather than body measurements, the cooking measurement converter handles cups, grams and millilitres by ingredient, and the temperature converter covers Fahrenheit, Celsius and gas marks.