One stone is 14 pounds, so 6.35 kg. British body weight is often quoted in stones and pounds together — convert the whole thing to pounds first, then use this.

Converters Weight

Pounds to kilograms

Pounds

Kilograms 0.45359

Decimals

Live · 1 lb = 0.45359237 kg exactly

Pounds you meet in the wild

1 lb 0.45359 kg

10 lb 4.53592 kg

25 lb 11.33981 kg

45 lb 20.41166 kg

100 lb 45.35924 kg

150 lb 68.03886 kg

200 lb 90.71847 kg

One pound equals 0.45359237 kilograms, a figure fixed by international agreement in 1959 rather than measured. Multiply pounds by 0.45359237 for kilograms. A useful mental check: halve the pounds and take off ten per cent, which puts 150 lb at about 67.5 kg against a true 68.04 kg.

How to convert pounds to kilograms

1 Type the weight in pounds.

2 Read the kilogram figure, and set the decimals you need with the buttons underneath.

3 Press ⇄ if you actually wanted kilograms to pounds.

Gym plates are the place this bites. American plates come in 45, 35, 25, 10, 5 and 2.5 pounds; European bars are loaded in 20, 15, 10, 5 and 2.5 kilograms. A 45 lb plate is 20.41 kg, not 20, so a bar loaded to "225 lb" is 102.06 kg rather than the round 100 kg somebody will quote you.

Questions

Where does 0.45359237 come from? −

The 1959 international yard and pound agreement, signed by six countries, defined the avoirdupois pound as exactly that many kilograms. It is a definition, so it has no error bar.

What about stones? +

Is the US pound the same as the UK pound? +

Why do airline limits look odd in kilograms? +

Sources

NIST Handbook 44 — Appendix C, general tables of units BIPM — The International System of Units (SI)

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