The Avoirdupois Weight Calculator converts between units in the avoirdupois system, the everyday weight system used for groceries, body weight and general trade in the United States and United Kingdom. Enter a value in pounds, ounces, grains, stone or hundredweight, and the tool returns the equivalent in any other avoirdupois unit, with the multiply or divide step shown.
Avoirdupois is the weight system most people already use without naming it: the ounce on a food label, the pound on a bathroom scale, and the stone used for body weight in the UK are all avoirdupois units, distinct from the troy system used for precious metals.
Convert between avoirdupois units
The avoirdupois system defines fixed ratios between its units: 16 ounces to a pound, 7,000 grains to a pound, 14 pounds to a stone, and 112 pounds to a UK hundredweight (100 pounds to a US hundredweight).
1 avoirdupois pound = 16 ounces = 7,000 grains = 453.59237 grams
1 stone = 14 pounds
1 UK hundredweight = 112 pounds
1 US hundredweight = 100 poundsWorked example: convert 5 pounds to ounces.
1. Multiply by 16. 5 × 16 = 80 ounces.
Convert pounds to grains
Grains are the smallest common avoirdupois unit, historically based on the weight of a single grain of barley, and still used today for bullet and arrow weights among other specialist applications.
grains = pounds × 7,000Worked example: convert 2 pounds to grains.
1. Multiply by 7,000. 2 × 7,000 = 14,000 grains.
Because a grain is so small, 7,000 of them make up just a single pound, the same 453.59237 grams as sixteen avoirdupois ounces.
Convert pounds to stone
Stone is a UK and Irish unit almost exclusively used for body weight, rarely appearing in other contexts.
stone = pounds ÷ 14Worked example: convert 154 pounds to stone.
1. Divide by 14. 154 ÷ 14 = 11 stone.
A weight given as "11 stone" with no remainder is a clean multiple of 14 pounds; most real body weights fall between whole stone values and are expressed as "stone and pounds," such as 11 stone 3 pounds.
Convert pounds to hundredweight
Hundredweight is used mainly in agriculture, shipping and some industrial contexts, and its definition differs between the US and UK.
US hundredweight (cwt) = pounds ÷ 100
UK hundredweight (cwt) = pounds ÷ 112Worked example: convert 500 pounds to US hundredweight.
1. Divide by 100. 500 ÷ 100 = 5 US cwt.
The same 500 pounds in UK hundredweight is 500 ÷ 112 ≈ 4.46 UK cwt, a meaningfully different figure, so specifying which hundredweight definition applies matters whenever the unit crosses the Atlantic.
Check common avoirdupois conversions
| Pounds | Ounces | Grains | Stone |
|---|---|---|---|
| 1 lb | 16 oz | 7,000 gr | 0.0714 st |
| 7 lb | 112 oz | 49,000 gr | 0.5 st |
| 14 lb | 224 oz | 98,000 gr | 1 st |
| 154 lb | 2,464 oz | 1,078,000 gr | 11 st |
Every column follows a fixed multiplication or division from the pound figure, since the avoirdupois system uses whole-number ratios throughout, unlike the mixed decimal factors that appear when crossing into metric units.
Distinguish avoirdupois from troy weight
Avoirdupois is not the only historical weight system still in limited use.
Troy weight, used for precious metals like gold and silver, defines its ounce and pound differently: a troy ounce (about 31.1 grams) is heavier than an avoirdupois ounce (about 28.35 grams), while a troy pound (12 troy ounces) is lighter than an avoirdupois pound (16 avoirdupois ounces).
Mixing the two systems without relabeling is a common source of pricing and measurement errors, particularly around precious-metal listings.
Convert ounces back to pounds
Reversing the pound-to-ounce relationship means dividing by 16 instead of multiplying.
pounds = ounces ÷ 16Worked example: convert 40 ounces to pounds.
1. Divide by 16. 40 ÷ 16 = 2.5 lb.
So 40 ounces equals exactly 2.5 pounds, the same 16-ounces-per-pound ratio used in the forward direction, applied as a division rather than a multiplication.
Convert grains back to pounds
Grains are the smallest common avoirdupois unit, so converting back to pounds means dividing by 7,000.
pounds = grains ÷ 7,000Worked example: convert 21,000 grains to pounds.
1. Divide by 7,000. 21,000 ÷ 7,000 = 3 lb.
So 21,000 grains equals exactly 3 pounds, confirming the same 7,000-grains-per-pound ratio used earlier on this page, whether converting forward from pounds or back from grains. Grain-based conversions like this one are most common in specialised fields such as ammunition and archery, where the small unit size gives finer precision than a fraction of an ounce would allow.
Frequently asked questions
How many ounces are in an avoirdupois pound?
16 avoirdupois ounces make one avoirdupois pound, the standard grocery and body-weight pound used in the US and UK.
How many grains are in a pound?
7,000 grains make one avoirdupois pound, making the grain the smallest common unit in the system.
How many pounds are in a stone?
14 pounds make one stone, a unit used almost exclusively for body weight in the UK and Ireland.
What is the difference between a US and UK hundredweight?
A US hundredweight is 100 pounds. A UK (long) hundredweight is 112 pounds. The two are not interchangeable without conversion.
Is avoirdupois the same as troy weight?
No. Avoirdupois and troy define their ounce and pound units differently. A troy ounce is heavier than an avoirdupois ounce, while a troy pound is lighter than an avoirdupois pound.
How do you convert stone and pounds to a single pound figure?
Multiply the stone count by 14 and add the remaining pounds. For example, 11 stone 3 pounds is (11 × 14) + 3 = 157 pounds.
Does this calculator convert avoirdupois units to metric units too?
Yes. Since 1 avoirdupois pound equals exactly 453.59237 grams, any avoirdupois figure can also be converted to kilograms or grams using that fixed factor.
Summary
The avoirdupois system links pounds, ounces, grains, stone and hundredweight through fixed whole-number ratios: 16 ounces and 7,000 grains per pound, 14 pounds per stone, and 100 or 112 pounds per hundredweight depending on the US or UK definition. Five pounds converts to 80 ounces or 35,000 grains, and 154 pounds converts to exactly 11 stone.
Because avoirdupois and troy define their units differently, converting between the two systems always needs the correct grams-per-unit factor rather than assuming a shared ounce or pound.