How to Convert Weight Units

Formula

result = value × factor, where factor = grams in one from unit ÷ grams in one to unit.

• value: the weight you want to convert, in the from unit.
• grams in one from unit: the size of the from unit in grams; 1,000 for the kilogram.
• grams in one to unit: the size of the to unit in grams; 453.59237 for the pound.
• factor: how many to units make one from unit.

The sizes are exact by definition (NIST Handbook 44, Appendix C; UK Weights and Measures Act 1985, Schedule 1):

The 1959 international yard and pound agreement defined the pound as exactly 0.45359237 kg. The ounce is 1/16 of a pound and the stone is 14 pounds.

Step-by-step example

Convert a body weight of 70 kilograms to pounds:

1. The from unit is the kilogram: 1 kg = 1,000 g. The to unit is the pound: 1 lb = 453.59237 g.
2. Find the factor: 1,000 ÷ 453.59237 ≈ 2.2046226219. One kilogram is about 2.2046 pounds.
3. Multiply the value by the factor: 70 × 2.2046226219 ≈ 154.323583529.
4. The result: 70 kg ≈ 154.32 lb. The same weight is about 11.02 stone and 2,469.18 ounces.

Common conversions

Common mistakes

• Mixing up the troy ounce and the everyday ounce. Gold and silver are priced in troy ounces, which are heavier than the everyday (avoirdupois) ounce. The weight converter uses only the avoirdupois ounce.
• Mixing up tons. The converter’s ton is the metric ton of 1,000 kg. The US short ton and the British long ton are different units and are not included.
• Reading stones and pounds as a decimal. “11 st 4 lb” is not 11.4 stone. Multiply the stones by 14, add the pounds, then convert the total in pounds.
• Mixing up mass and force. What everyday language calls weight is mass. The pound-force (lbf) and the newton are units of force; the weight converter does not convert them.