Convert kilograms, grams, pounds, ounces, tons and stones.
Conversion factors: 1 kg = 1 000 g = 1 000 000 mg = 0.001 t = 2.20462 lb = 35.27396 oz = 0.157473 st. The pound is exactly 0.45359237 kg by international agreement.
Mass and weight are everywhere, and the world stubbornly refuses to use one unit. Cooking recipes mix grams (metric) and ounces (US/UK); fitness uses kilograms or pounds depending on country; freight uses metric tons or US/UK tons; jewellery weighs in grams or grains; UK body weight historically uses stones. A misread "1 lb" as "1 kg" can ruin a recipe, mis-dose a medication, or invalidate a freight calculation. This calculator does the seven most common conversions in both directions, with enough precision to keep recipe and engineering use cases happy. It treats the kilogram as the canonical unit (the SI base) and converts in two passes — input → kg → all other units — so the math is symmetric and round-trip stable.
Conversion factors (each unit's value in kilograms): - 1 mg = 1 × 10⁻⁶ kg - 1 g = 1 × 10⁻³ kg - 1 kg = 1 kg (canonical) - 1 t (metric ton) = 1 000 kg - 1 oz (avoirdupois) = 0.028 349 523 125 kg (exact) - 1 lb (avoirdupois) = 0.453 592 37 kg (exact, international agreement 1959) - 1 st (stone) = 6.350 293 18 kg (= 14 lb, exact)
A value V in input unit U converts to V × factor(U) kilograms, then divides by factor(target) for any other unit. The pound and ounce values are exact by international agreement (the international avoirdupois pound was defined in 1959 as exactly 0.453 592 37 kg); the metric units are exact by SI definition. The metric ton is exactly 1 000 kg by SI prefix. Floating-point rounding on display, not in the conversion factor.
Enter the value and pick the input unit from the dropdown. The result panel shows the same mass in all seven units — kg, g, mg, t, lb, oz, stone — at once. The four most common (kg, g, lb, oz) are headline KPIs; the rarer three (mg, t, stone) appear as smaller stats below.
A 70-kg adult. - 70 kg = 70 000 g = 70 000 000 mg = 0.07 t = 154.32 lb = 2 469.13 oz = 11.024 stone.
A US 50-lb dog-food bag. - 50 lb × 0.453 592 37 = 22.68 kg = 22 679.6 g = 800 oz = 3.571 stone.
A 1-tonne pallet. - 1 t = 1 000 kg = 2 204.62 lb ≈ 35 274 oz.
These are exact through the lb/oz conversions; the cap of "exact" decimals depends on the user's display precision (the calc rounds to the site-wide locale rules — typically 2 decimals for kg/lb/oz/stone, 3 for grams when small).
Avoirdupois vs troy vs apothecary. The pound and ounce here are avoirdupois — the everyday US/UK system (16 oz = 1 lb, 1 lb = 0.4536 kg). The troy system, used for precious metals, has a different ounce (1 troy oz = 31.103 g vs 1 avoirdupois oz = 28.350 g). The apothecary ounce is yet another. If you're weighing gold or pharmaceuticals, this calc is the wrong tool — use a precious-metals or pharmacy-units converter.
US ton vs UK ton vs metric ton. The US ton ("short ton") is 2 000 lb = 907.185 kg. The UK ton ("long ton") is 2 240 lb = 1 016.05 kg. The metric ton (used here, written t or tonne) is exactly 1 000 kg. They differ by ~10 %, enough to matter in shipping. Confirm which "ton" your invoice is talking about.
Mass vs weight. The calc converts mass (the inertial property), not weight (mass × local gravity). On Earth's surface they're proportional and people use the words interchangeably; on the Moon a 70-kg mass weighs only ~117 N (vs 686 N on Earth). For physics use cases, treat the result as mass and apply the gravitational acceleration separately.
Stone, in clinical settings. The UK NHS still records adult body weight in stones-and-pounds in many older systems. 11 stone 4 lb = 11 × 14 + 4 = 158 lb = 71.66 kg. The calc returns plain decimal stones (e.g. 11.024); convert to "stones and pounds" by separating the integer and fractional parts (0.024 stone × 14 = 0.34 lb).
Grain (the smallest avoirdupois unit) is not exposed here — it's used almost exclusively for ammunition propellant and a few pharmacy tasks. 1 grain = 1/7 000 lb ≈ 64.799 mg.