How this calculator works
These calculators convert mass, which is measured in kilograms in SI. Everyday use of "weight" often means mass, but physical weight is a force that depends on local gravity. No force or gravity calculation is performed here. The international pound is defined in kilograms by the 1959 agreement, while metric prefixes define the smaller and larger SI units. The ounce here is always the avoirdupois ounce, never the troy ounce of precious metals and never the fluid ounce, which measures volume.
Formula
result = value × F(from) ÷ F(to), where F is the exact kilograms per unit: 1 lb = 0.45359237 kg, 1 oz = 0.028349523125 kg, 1 st = 14 lb = 6.35029318 kg, 1 mg = 0.000001 kg, 1 g = 0.001 kg, 1 t = 1000 kg.
Worked example
1 kg to pounds: 1 ÷ 0.45359237 = 2.20462 lb. 8 oz to grams: 8 × 28.349523125 = 226.796 g. 11 st to kilograms: 11 × 6.35029318 = 69.8532 kg.
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Frequently asked questions
Are these weight or mass units?
Mass. A scale commonly reports mass in kilograms or pounds. Physical weight is a force measured in newtons and depends on gravity; this converter does not calculate it.
Is the ounce here the same as a troy ounce?
No. This converter uses the avoirdupois ounce of exactly 28.349523125 g. A troy ounce, used for precious metals, is exactly 31.1034768 g.
Can I convert fluid ounces here?
No. The ounce on this page is a mass unit. Fluid ounces measure volume and belong on the volume converter.