Free mass calculator
Convert mass between kilograms and pounds — and grams, ounces, metric tons, and more — using the exact NIST conversion factor (1 lb = 0.45359237 kg) with instant results.
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Conversions use the NIST exact factor: 1 lb = 0.45359237 kg. Results are for informational purposes only.
Results are estimates. Consult a professional.
How the mass converter works
The mass converter applies a single exact conversion factor to move between any two units of mass. Every relationship traces back to one anchor: the international avoirdupois pound, defined in 1959 as exactly 0.45359237 kilograms by agreement among the English-speaking nations. Because that definition is exact — not approximate — every conversion in this calculator is exact too, limited only by the digits you enter.
Worked example: 75 kg to pounds
Sofia is travelling to the United States and needs her 75 kg body weight in pounds for a medical form. The conversion factor is exact: 1 kg = 1 ÷ 0.45359237 lb = 2.20462262... lb.
Common kg to lb conversions
The table below covers the most-looked-up body weights and object masses. Every figure uses the exact NIST factor, rounded to three decimal places.
| Kilograms (kg) | Pounds (lb) | Grams (g) | Ounces (oz) |
|---|---|---|---|
| 0.5 | 1.102 | 500 | 17.637 |
| 1 | 2.205 | 1,000 | 35.274 |
| 5 | 11.023 | 5,000 | 176.370 |
| 10 | 22.046 | 10,000 | 352.740 |
| 25 | 55.116 | 25,000 | 881.849 |
| 50 | 110.231 | 50,000 | 1,763.698 |
| 75 | 165.347 | 75,000 | 2,645.547 |
| 100 | 220.462 | 100,000 | 3,527.396 |
Values computed from the exact conversion 1 lb = 0.45359237 kg (NIST SP 811). Ounces are avoirdupois: 1 oz = 1/16 lb.
When and why you need a mass converter
Switching between kilograms and pounds comes up constantly in everyday life and professional work. The converter is useful any time units cross a country boundary or a professional context.
- Travel and healthcare — US medical forms ask for weight in pounds; most of the world uses kilograms. A quick conversion avoids errors on intake forms and medication dose calculations.
- Fitness and nutrition — gym equipment, protein targets, and calorie-calculator inputs vary by country. Knowing your weight in both units means you can use any app or calculator without guessing.
- Shipping and logistics — carriers in the US use pounds for domestic parcels; international shipments require kilograms. Exceeding a weight threshold by even a small amount can shift you into the next rate bracket.
- Cooking and recipes — US recipes quote butter, meat, and produce in pounds and ounces; metric recipes use grams. Converting between the two keeps dish quantities accurate.
- Science and engineering — scientific measurements use SI units (kg, g, mg); older technical documents and some US engineering standards still quote pounds-mass (lbm). The same NIST factor applies.
Accuracy and limitations
The conversion factor itself is exact — 1 lb = 0.45359237 kg by international definition, with no rounding in the underlying number. The calculator carries the full precision of that factor, so results are limited only by the number of digits you enter, not by the formula.
Two things to keep in mind. First, mass vs weight: in everyday use the two words are interchangeable, but in physics they are not. Mass is the amount of matter (measured in kg); weight is the gravitational force on that mass (measured in newtons). This calculator converts mass. Second, avoirdupois vs troy vs apothecary pounds: this calculator uses the standard avoirdupois pound (the everyday pound in the US and UK). Troy pounds (used for precious metals) and apothecary pounds are different units — one troy pound is only about 0.373 kg. When converting gold, silver, or gemstones, confirm which pound the source uses.
Mass unit definitions
About this mass converter
This calculator runs entirely in your browser. Nothing you enter is sent to any server — the conversion happens instantly on your device, and no data is stored or logged.
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