Mass Calculator
Mass Unit Conversion
Ready for Calculation
Enter a mass value and unit to see conversions across all common mass units.
Understanding Mass Units
Mass is the amount of matter in an object, measured consistently whether on Earth or in orbit. Different regions and industries favor different units — metric grams and kilograms dominate science and most of the world, while pounds, ounces, and stone remain common in the US and UK.
Metric System
The metric system scales by powers of ten — 1,000 mg = 1 g, and 1,000 g = 1 kg — making unit conversion straightforward arithmetic.
Imperial & US Customary
16 ounces make a pound, 14 pounds make a stone (UK), and a US ton is 2,000 pounds — distinct from the UK "long ton" of 2,240 pounds.
Mass vs. Weight
Mass is an intrinsic property of matter and stays constant everywhere in the universe. Weight is the force gravity exerts on that mass, and it changes depending on where you are — on the Moon, your mass is unchanged but your weight is about 1/6th of what it is on Earth.
See Our Weight Calculator
For a comparison of your weight (a force) across different planets, see our dedicated Weight Calculator.
Key Takeaways
- Pure Unit Conversion: This tool converts mass units only — it does not assess a healthy weight range, see our BMI or Ideal Weight calculators for that.
- Metric Ton vs. US Ton: A metric ton (1,000 kg ≈ 2,204.6 lb) is different from a US ton (2,000 lb ≈ 907.2 kg) — always confirm which one applies.
- Precision Matters: For scientific or medical use, keep several decimal places when converting between very different unit scales (e.g., mg to kg).