Free online weight & mass converter. Convert pounds to kilograms, ounces to grams, stones, metric tons, and 8 more units — instant results, visual chart, and conversion history.
Imperial • Metric • 9 units
Track your weight in both lbs and kg for international gym equipment, nutrition labels, and doctor visits.
Convert package weights for USPS, UPS, FedEx and international carriers that use kg.
Convert grams and ounces for international recipes — European recipes always use metric weights.
Weight conversion is one of the most frequently searched calculations in the United States. The reason: Americans track body weight in pounds (lbs) while most of the world — and all scientific, medical, and pharmaceutical contexts — use kilograms. A person weighing 180 pounds weighs 81.65 kg. The simple mental shortcut: divide pounds by 2.2 to get kilograms (exact factor is 2.20462). To go from kg to lbs, multiply by 2.2046.
Ounces to grams is critical for cooking and postal purposes. 1 ounce (avoirdupois) = 28.3495 grams. A common confusion: the "fluid ounce" is a volume measurement, not a weight — our cooking converter handles fluid ounces separately. For dry ingredients in recipes: 1 oz = 28.35 g, 4 oz = 113.4 g (quarter pound), 8 oz = 226.8 g (half pound), 16 oz = 453.6 g = 1 pound.
Stone is a weight unit used primarily in the UK and Ireland for expressing body weight. 1 stone = 14 pounds = 6.35029 kg. If someone in the UK says they weigh "12 stone 4 lbs", that's 172 lbs or 78.02 kg. Short ton (US) = 2,000 lbs = 907.185 kg. Long ton (UK) = 2,240 lbs = 1,016.05 kg. Metric ton (tonne) = 1,000 kg = 2,204.62 lbs.
100 lbs = 45.36 kg. 120 lbs = 54.43 kg. 150 lbs = 68.04 kg. 180 lbs = 81.65 kg. 200 lbs = 90.72 kg. 250 lbs = 113.4 kg. To convert: ÷2.2046.
1 oz = 28.35 g. 4 oz = 113 g. 8 oz (½ lb) = 227 g. 1 lb = 454 g. 1 stick butter = 4 oz = 113 g. 1 cup flour ≈ 120 g. 1 cup sugar ≈ 200 g.
USPS first class max: 13 oz. Flat rate box: up to 70 lbs. International priority mail: priced by 0.5 kg increments. Standard letter: 1 oz = 28 g max.
45 lb Olympic barbell = 20.41 kg. 45 lb plate = 20.41 kg. 25 lb plate = 11.34 kg. 2.5 lb = 1.13 kg. Most commercial gym dumbbells: labeled in lbs and kg.
Mass conversions hinge on one exact definition: the international avoirdupois pound is precisely 0.45359237 kilograms, agreed in 1959. Everything else follows — 16 ounces to the pound, 14 pounds to the stone, 2,000 pounds to the US short ton and 2,240 to the British long ton. The tonne, spelled that way, is a metric 1,000 kg and sits between the two, which is a genuine source of commercial confusion. Note also that mass and weight are distinct: the kilogram measures mass, while the pound-force and newton measure weight, a force that varies with gravity.
kilograms = value × factor_fromresult = kilograms ÷ factor_to1 lb = 0.45359237 kg · 1 oz = 28.349523125 g · 1 st = 6.35029318 kgwhere:
Assumptions: Avoirdupois units throughout. Troy weights for gold and silver, and apothecary weights, use different ounces and are not interchangeable with these.
A body weight of 175 lb rendered in the two systems the rest of the world uses.
Result175 lb = 79.38 kg = 12 st 7 lb
The stone survives almost exclusively for body weight in the UK and Ireland; medical records there are kept in kilograms. Fitness apps that silently mix pounds and kilograms produce a 2.2× error, which is large enough to be obvious but small enough to be missed in a log.
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