Mass & Weight Converter

Mass measures the amount of matter in an object, independent of gravity. It is one of the seven SI base quantities, and the kilogram — the SI base unit of mass — has been defined since 2019 by fixing the Planck constant to exactly 6.62607015 × 10⁻³⁴ J·s.

Key exact relationships

• 1 kilogram = 1000 grams exactly
• 1 metric ton = 1000 kilograms exactly
• 1 international pound = 0.45359237 kg exactly
• 1 ounce = 1/16 pound = 28.349523125 g exactly
• 1 stone = 14 pounds exactly
• 1 US short ton = 2000 pounds exactly
• 1 UK long ton = 2240 pounds exactly
• 1 troy ounce = 480 grains = 31.1034768 g exactly
• 1 carat = 200 mg exactly

Mass vs. weight

In everyday usage, "weight" and "mass" are used interchangeably. In physics, they are different quantities: mass is invariant, while weight is the force that gravity exerts on a mass. On Earth's surface the two are proportional, which is why the everyday confusion rarely causes problems. For scientific and engineering work, use mass (kg) for the amount of matter and weight (N) for the gravitational force.

See the Mass vs. Weight guide for more detail.