How this works
Pick a unit, type a value, and see the equivalent weight in every other common unit at once. Metric covers milligrams up to tonnes; imperial covers ounces up to stones (popular in the UK for body weight). All conversions use the international avoirdupois pound (1 lb = 0.45359237 kg exactly) — the same definition used by NIST, ISO, and every metric/imperial conversion tool worth trusting.
The formula
Factors used: 1 mg = 1e-6 kg, 1 g = 0.001 kg, 1 t = 1000 kg, 1 oz = 0.0283495231 kg, 1 lb = 0.45359237 kg, 1 st = 6.35029318 kg. Every conversion routes through kilograms as the canonical unit so rounding never compounds across hops.
Example calculation
- Enter 70 kg. The calculator first treats kg as the canonical unit: kilograms = 70.
- Then divides by each target factor: 70 / 0.45359237 ≈ 154.32 lb; 70 / 6.35029318 ≈ 11.02 st.
- So 70 kg ≈ 154.32 lb ≈ 11 st 4.5 lb — useful when reading UK body-weight conventions.
Frequently asked questions
Why are stones still used in the UK?
Mostly tradition. The UK officially uses metric for trade and science, but body weight in everyday speech is almost always quoted in stones and pounds — "I weigh 11 stone 4." 1 stone = 14 pounds = ~6.35 kg. Useful range: 7-20 stones covers virtually every adult, which is a more compact verbal range than 45-127 kg.
Is a US ton the same as a metric tonne?
No — three different "tons" exist. Metric tonne (this calculator) = 1,000 kg. US short ton = 2,000 lb = 907.185 kg. UK long ton = 2,240 lb = 1,016 kg. We only support the metric tonne to keep the UI honest; if a US recipe or shipping document quotes "tons", check whether it means short tons.
Why does kg → lb give a number with so many decimals?
Because the lb-kg conversion factor is irrational in decimal — 1 lb = 0.45359237 kg means 1 kg = 2.2046226218... lb, which never terminates cleanly. The calculator shows up to 4 decimals for everyday values; if you only need 1 or 2 decimals for a quick mental check, just round.