Weight & Mass Converter

The kilogram is the SI base unit of mass. All other units here are defined in exact relation to it: 1 lb = 0.45359237 kg and 1 oz = 0.028349523125 kg (exact, NIST SP 811). Type a value in any unit and every other unit updates live; click any result to make it the new input.

The formula

All conversions route through the kilogram as base:

target = value × (fromUnit_to_kg / toUnit_to_kg)

For pounds to kilograms:

kg = lb × 0.45359237

For kilograms to pounds:

lb = kg × (1 / 0.45359237) = kg × 2.20462

Practical examples

Example 1 — Gym weight plates (kg to lbs)

A barbell is loaded to 100 kg. The athlete needs the equivalent in pounds for a US competition record.

100 × 2.20462 = 220.46 lb

Example 2 — Grocery shopping (grams to ounces)

A deli counter in Europe sells 350 g of cheese. A US recipe calls for the weight in ounces.

350 × (1/28.3495) = 350 ÷ 28.3495 = 12.35 oz

Example 3 — UK body weight (stone to kilograms)

A UK health form records a patient's weight as 12 stone 4 lb. Convert to kilograms.

12 × 6.35029 = 76.20 kg
4 × 0.45359 = 1.81 kg
Total = 78.01 kg

Common mistakes

Mistake 1 — Confusing metric tonne and US short ton

The metric tonne (1000 kg ≈ 2204.6 lb) and the US short ton (2000 lb ≈ 907 kg) are different units by about 10%. This converter uses the metric tonne. Always specify which "ton" a source means.

Mistake 2 — Treating the stone as a UK-only curiosity

Stone is still actively used for body weight in the UK and Ireland. Gym equipment, GP charts, and pharmacies routinely display weights in stone. International health forms should always convert to kilograms.

International and regional variations

Quick reference: common weight conversions