Article — Lbs to Grams Converter
Pounds to grams: convert lbs to g exactly
One pound equals exactly 453.59237 grams. That number is not a measurement — it is a treaty value, fixed by the 1959 International Yard and Pound Agreement between the United States, United Kingdom, Canada, Australia, New Zealand, and South Africa. Every modern pound-to-gram conversion uses this exact factor, and any value with more than five decimal places of difference is using an older national pound that the 1959 treaty replaced.
The calculator at the top of this page handles both directions. The text below covers when the exact figure matters, when 454 g is close enough, and why a quarter pound of beef and a stick of butter weigh exactly the same.
The exact factor: 453.59237
One pound is defined as 0.45359237 kilograms, which equals 453.59237 grams. That is an exact value, not a rounded one. Before 1959 each English-speaking country had a slightly different pound — the US used a pound defined against a Bureau of Standards metal prototype, the UK used the imperial pound defined in an 1878 Act, and Canada and Australia tracked the UK with small drift. The differences were measured in micrograms but caused problems for trade and science.
The 1959 agreement fixed one value. The pound is now a kilogram derivative, just as the inch is a millimetre derivative (25.4 mm exactly). When you read "1 lb = 453.59237 g" anywhere in modern reference material, that is the legal definition, not a measurement someone took.
The number 0.45359237 is one of seven defined exact conversion factors in the SI system between metric and US customary units. The others fix the yard at 0.9144 m, the inch at 25.4 mm, the foot at 0.3048 m, and three units of volume. All seven were set in 1959 by treaty. NIST publishes them in Special Publication 811, Appendix B, as the official US conversion reference.
How to convert pounds to grams
To convert pounds to grams, multiply by 453.59237. To go from grams back to pounds, divide by the same number. That is the entire formula. The calculator above does both directions in real time, but you can also do it by hand:
g = lbs × 453.59237 (exact)lbs = g ÷ 453.59237 (exact)g ≈ lbs × 454 (0.1% error)lbs ≈ g ÷ 454 (0.1% error)For most practical purposes — cooking, postage, body weight — 454 g per pound is close enough. Pharmacy, legal weights, and scientific work use the full 453.59237. The calculator lets you set precision from 0 to 6 decimals so you can pick the right level for the job.
Mental math shortcuts
The cleanest mental shortcut is "multiply by 450, then add 1%." For 3 pounds: 3 × 450 = 1350, plus 1% of 1350 = 13.5, giving 1363.5 g. The true value is 1360.78 g. The shortcut is off by 0.2%. Fine for the kitchen, not for the lab.
The reverse shortcut — grams to pounds — is "divide by 450, then subtract 1%." 1000 g ÷ 450 = 2.22, minus 1% of 2.22 = 0.022, giving 2.20 lb. True value: 2.2046 lb. Same 0.2% error band.
If you only need ballpark numbers, "lbs × 2.2 = kg × 10" works for converting whole pounds into rough grams. A 5 lb bag of flour is "about 2.3 kg" or "about 2300 g," because 5 × 2.2 / 10 = 1.1, and then × 1000 = 2200 g (true: 2268 g). The shortcut understates by 3% but lands you in the right ballpark.
Cooking and the butter-stick problem
American recipes use pounds and ounces. European recipes use grams. Translation between the two is the most common reason people search for this conversion, and butter is the most common ingredient that needs it.
In the US, butter sells in "sticks." Each stick is a quarter pound — 113.4 g, half a cup, or 8 tablespoons. A standard package of US butter has four sticks, totalling 1 lb (453.6 g). European butter blocks are usually sold as 250 g packages, which is 0.551 lb. UK butter often comes in 250 g blocks too, occasionally in 454 g (a clean pound). When a US recipe asks for "two sticks of butter," that is 226.8 g, not 250 g — close but not identical.
A common substitution error in international recipe conversion. Two US sticks = 226.8 g. A European 250 g block has 23 g more. That's 10% more fat than the recipe expects, enough to throw off the texture of a pastry or a buttercream frosting. If a US recipe calls for 2 sticks and you have a 250 g block, use about 91% of it (227 g).
Meat is the second-most-common cooking case. "1 pound of ground beef" in any US recipe means 453.6 g raw. The same applies to chicken, pork, and fish. Cooked weight drops by 20-30%, but recipes always state raw weight unless they specify "cooked."
Avoirdupois vs. troy pounds
There are two pounds. The avoirdupois pound is the everyday pound — used for groceries, body weight, postage, and basically everything. It weighs 453.59237 g and contains 16 ounces.
The troy pound is used for precious metals only. It weighs 373.24 g and contains just 12 troy ounces. A troy ounce (31.1035 g) is heavier than an avoirdupois ounce (28.3495 g), but the troy pound is lighter overall because it has fewer ounces in it. It is the kind of historical wrinkle that catches people out exactly once.
- Avoirdupois pound = 453.59 g (groceries, body weight, freight)
- Avoirdupois ounce = 28.35 g (16 per pound)
- Troy pound = 373.24 g (precious metals only)
- Troy ounce = 31.10 g (12 per troy pound)
- Stone (UK) = 14 lbs = 6.35 kg (still used for body weight in Britain)
- Hundredweight (US) = 100 lbs = 45.36 kg (livestock, agriculture)
- Long ton (UK) = 2240 lbs = 1016 kg
- Short ton (US) = 2000 lbs = 907 kg
Shipping and postage
US shipping uses pounds. International airlines use kilograms. The conversion matters when you are checking weight limits at a counter that uses a different system than the one you packed for.
USPS Priority Mail caps individual parcels at 70 lb (31.75 kg). UPS Ground accepts up to 150 lb (68.04 kg) per box. Most international airlines cap economy checked bags at 23 kg (50.71 lb) and premium bags at 32 kg (70.55 lb). The 23 kg limit is actually 50 lbs — the airlines just round the limit to "50 lbs" on the US side.
If you weigh in pounds at home and need to hit a kilogram limit at the airport, leave yourself a buffer. Bathroom scales drift up to 2% over time, and check-in scales are calibrated more strictly. A bag that reads "exactly 50 lb" at home often reads 50.5-51 lb at the gate, which can trigger overweight fees of $100 or more.
Where the number came from: 1959
Before 1959, the world had at least four pounds. The US pound was defined by a brass prototype kept at the National Bureau of Standards. The UK imperial pound was defined by an Act of Parliament in 1878 and tied to a separate platinum prototype kept in London. Canada and Australia tracked the UK loosely, and small drifts accumulated over decades. The differences were tiny — a few parts per million — but they were enough to cause discrepancies in trade contracts and scientific measurements.
In 1958, the directors of the national standards labs from six English-speaking countries met to agree on a fix. The result, signed on 1 July 1959, defined the pound as exactly 0.45359237 kilograms. That value was chosen because it sat almost exactly between the US and UK pounds at the time, splitting the difference. From that day forward, "pound" had one legal meaning across the English-speaking world.
The 1959 agreement covered the pound and the yard but kept one historical exception: the US Survey Foot. US land surveys, property boundaries, and geodetic measurements used a slightly different foot (1200/3937 m, about 2 parts per million longer than the international foot). The Survey Foot was finally retired by NIST on 1 January 2023 — 64 years after the rest of US measurement had switched. The change affected millions of property deeds, which now use the international foot exclusively.
Common mistakes
Mixing up avoirdupois and troy. If you weigh 10 ounces of gold on a kitchen scale (avoirdupois) and price it at the troy spot rate, you understate the value by about 10%. Always confirm which ounce you are working with for precious metals.
Confusing pounds with grains. A grain (gr) is an old apothecary unit equal to 0.0648 g. One pound contains 7000 grains. The unit still appears in ammunition (bullet weights) and pharmacy (aspirin tablets historically dosed in grains). Do not confuse a 200-grain bullet with a 200-gram one — the difference is a factor of 15.
Net vs. gross weight. Package labels show net weight — the weight of the contents alone. The gross weight includes packaging. A "1 lb" loaf of bread is 453.6 g of bread, but the bag and label add a few extra grams. For shipping, gross weight matters; for cooking, net weight does.
Rounding 1 lb to 450 g. Fine for casual cooking. Wrong for postage and any commerce where weight determines price. A 100 lb shipment computed at 450 g per pound understates the real mass by 359 g — small per pound, but a kilo of phantom weight over a full pallet.