What is a mass converter?
A mass converter translates between units of weight — kilograms, grams, pounds, ounces, tons. Different countries use different defaults: India and most of the world use metric (kg, g); the US/UK use pounds and ounces; jewelers use troy ounces (subtly different from regular ounces).
Supported units
| Unit | Symbol | Equivalent |
|---|---|---|
| Kilogram | kg | Base unit (SI) |
| Gram | g | 0.001 kg |
| Milligram | mg | 10⁻⁶ kg |
| Microgram | µg | 10⁻⁹ kg |
| Pound | lb | 0.45359237 kg |
| Ounce | oz | 0.0283495 kg |
| Stone | st | 6.35029 kg |
| Metric ton | t | 1,000 kg |
| US short ton | — | 907.185 kg |
| UK long ton | — | 1,016.05 kg |
How conversion works
target_value = source_value × source_factor / target_factor
Each unit has a factor in kg. The calculator routes all conversions through kg internally.
Worked example
Convert 165 lb (US body weight) to kg:
165 × 0.45359 = 74.84 kg
Convert 5 oz (recipe ingredient) to grams:
5 × 28.3495 = 141.75 g
Mental math shortcuts
| Approximation | Use when |
|---|---|
| 1 kg ≈ 2.2 lb | Body weight, gym weights |
| 1 lb ≈ 0.45 kg | Imperial to metric |
| 1 oz ≈ 28 g | Cooking, small weights |
| 1 stone = 14 lb = 6.35 kg | UK body weight |
| 1 ton (metric) = 1,000 kg | Bulk shipping |
| Body weight: divide pounds by 2.2 for kg | Quick mental conversion |
Common pitfalls
- Mass vs weight. Mass is the amount of matter (constant). Weight is force = mass × gravity (varies by planet). On Earth, 1 kg "weighs" 9.81 N. Casually, "weight" = "mass" but in physics they're distinct. See Weight Calculator.
- Troy ounce ≠ regular ounce. Jewelry / precious metals use troy ounce = 31.1035 g. Cooking / postal uses regular (avoirdupois) ounce = 28.3495 g. A "10-ounce gold bar" weighs 311 g (troy), not 283 g (avoirdupois).
- Ton variants. Metric ton = 1,000 kg. US short ton = 907 kg. UK long ton = 1,016 kg. Always specify which.
Considerations
- Body weight in different cultures. US/UK: pounds. India: kg. Some UK forms: stones + pounds. Most modern Indian doctors use kg exclusively.
- Postage and shipping. International couriers often quote both kg and lb. Customs use kg.
- Precision matters in pharmacy. Drug dosages in mg or µg — getting the factor of 1000 wrong is a medical error.
Limitations
- The calculator doesn't auto-detect troy vs avoirdupois ounce — pick "ounce" for the standard (cooking/postal) version. For troy ounce, multiply weight by 31.1035 / 28.3495 = 1.097 manually.
- Floating-point precision may show trailing decimals; take 3-4 decimals for practical use.
Related calculators
- Length — distance conversions
- Volume — liquid measurements
- BMI — uses kg for body weight
- Density — mass / volume
- Weight (physics) — mass × gravity = force
- Force — Newtons
Final note. Mass conversions trip up cooks (oz vs g recipes), travelers (luggage weight limits in kg vs lb), and jewelers (troy vs avoirdupois). The fix: always confirm which unit system applies, then convert once with this tool rather than juggling mental approximations.