Weight (Mass) Converter

Which weight units does it convert?

Thirteen units of mass and two combined forms: micrograms, milligrams, grams, kilograms and metric tons; ounces, pounds, pounds and ounces, and US short tons; stone, stone and pounds, and UK long tons; grains, carats and troy ounces. Type a weight once and the table lists it in each of them (micrograms only when you pick them), every value marked exact or rounded. Body weights come out as stone and pounds, baby and parcel weights as pounds and ounces, and a chart lists the values around yours. Add a price to see what it comes to per gram, pound, ton or troy ounce.

How to use it

• Weight: the number to convert, in the unit you pick under From. You can type thousands separators or e-notation, such as 1,250 g or 3e-6 t.
• Pounds and ounces or Stone and pounds: appear when From is one of these combined units. Type 7 lb 6 oz, 7lb 6oz or 7-6, and 11 st 4 lb, 11st 4 or 11-4. More than 15 oz or 13 lb carries over, so 7 lb 18 oz is read as 8 lb 2 oz, and the line under the box says so.
• From and To: the unit on your scale, label or invoice, and the unit you need. The three tons are named in full: short tons (US, 2,000 lb), long tons (UK, 2,240 lb) and metric tons or tonnes (1,000 kg). Micrograms come after kilograms.
• Significant figures: Auto shows up to 12 significant figures and whole numbers in full, so exact values such as 0.45359237 appear complete. Choose fewer for a shorter answer.
• Round the oz or lb part: how pounds and ounces and stone and pounds results are rounded: to whole ounces or pounds, to 0.1 or to 0.01, as the examples in the list show.
• Add a price per unit: tick it to enter a Price per unit, the price of one From unit (of one pound when From is pounds and ounces or stone and pounds).

Under the answer, Swap converts the other way (72.5 kg to pounds becomes 72.5 lb to kilograms), and choosing a unit name in the table moves that unit into the headline. The five Try buttons load a baby’s weight, a UK body weight, a troy ounce of gold, a short ton and a kitchen amount. What you type stays in your browser; a link with your numbers exists only if you press Share link and copy it.

How many pounds are in a kilogram?

About 2.20462 lb, because the pound is defined as exactly 0.45359237 kg. The national standards laboratories of the United States, the UK, Canada, Australia, New Zealand and South Africa agreed on that value in 1959, and the ounce, stone and tons are all defined from the pound:

So pounds, ounces, stone, tons and troy ounces convert to metric as short exact decimals, while the other way the division almost never ends: 1 kg ≈ 2.20462262185 lb and 1 g ≈ 0.0352739619496 oz. That is why the table labels each value Exact or Rounded: pounds to kilograms is exact, kilograms to pounds almost never is.

Weight conversion formula

Each unit has a fixed mass in kilograms, $f$. To convert a mass $m$ from one unit to another:

• $m_{\text{from}}$ is the weight you have, $m_{\text{to}}$ the weight in the new unit.
• $f_{\text{from}}$ and $f_{\text{to}}$ are the two units’ masses in kilograms: 0.45359237 for a pound, 0.028349523125 for an ounce, 0.001 for a gram.

For pounds to kilograms that is $m \times 0.45359237$, and for kilograms to pounds $m \div 0.45359237$. The steps under the result always use the exact factor, never a rounded one such as 2.2.

Worked example: 72.5 kg in pounds, stone and ounces

1. Kilograms to pounds: 72.5 ÷ 0.45359237 = 159.835140084 lb. The quotient never terminates, so the headline rounds it to 12 significant figures.
2. Stone and pounds: 159.83514008404 ÷ 14 = 11.4167957203, so 11 st, which is 154 lb. The rest is 159.83514008404 − 154 = 5.83514008404 lb, shown to 0.1 lb as 11 st 5.8 lb. (The pounds carry two more decimals here so the subtraction adds up as written.)
3. Pounds and ounces: 72.5 kg is 2,557.3622413446 oz; 2,557.3622413446 − 159 × 16 = 13.3622413446 oz, so 159 lb 13.4 oz.
4. The table gives the same weight as 72,500 g and 0.0725 t (both exact), 0.079917570042 short tons and 0.0713549732518 long tons.

Rounding 2.20462 to 2.2 would give 72.5 × 2.2 = 159.5 lb, 0.335 lb (0.21%) too light.

Kilograms to pounds, and pounds to kilograms

Kilograms to pounds are rounded (6 significant figures here); pounds to kilograms are exact, because each is a whole number times 0.45359237.

The chart under each result does the same for any pair of units, in eleven steps around your number, and downloads as CSV.

Kilograms to stone and pounds

In the UK and Ireland body weight is often given in stone and pounds. A stone is 14 lb, exactly 6.35029318 kg. To go from kilograms, divide by 0.45359237 to get pounds, then take out whole stones of 14 lb; the pounds left over are the second number.

For a weight such as 11 st 4 lb, choose stone and pounds under From: 11 × 14 + 4 = 158 lb, and 158 × 0.45359237 = 71.66759446 kg.

Pounds and ounces (baby weights and parcels)

In the US and UK, birth weights are often quoted in pounds and ounces, and many parcel scales show them too. There are 16 oz in a pound, so 7 lb 6 oz is 7 × 16 + 6 = 118 oz, and 118 × 28.349523125 g = 3,345.24372875 g, or 3.345 kg. The other way, a 3.4 kg baby is 7 lb 7.9 oz. Ounces to grams are always exact:

In the kitchen, 100 g is 3.5274 oz and 250 g is 8.81849 oz. These are ounces of weight; a US fluid ounce measures volume and is a different unit.

Short ton vs long ton vs metric ton

“Ton” names three different weights, up to 12% apart. The US short ton is 2,000 lb, the UK long ton 2,240 lb, and the metric ton (spelled tonne outside the US) 1,000 kg, which is about 2,204.62 lb. Shipping, freight and commodity prices can use any of them, so check which one a figure means before you convert it.

Whenever you pick a ton under From or To, the converter repeats this warning above the steps, and the tiles under the answer show the weight in the tons you didn’t pick.

Troy ounces vs ounces (gold and silver)

Precious metals are weighed in troy ounces of 480 grains, exactly 31.1034768 g. The ordinary (avoirdupois) ounce used for food and parcels is 437.5 grains, 28.349523125 g, so a troy ounce is 1.09714285714 ordinary ounces, about 9.7% heavier.

A 1 kg bar holds 32.1507 troy ounces but 35.274 ordinary ounces. Troy ounces are the ones to use for bullion; a gemstone’s carat is a different unit again, 200 mg.

Mass vs weight: what this converter measures

Every unit here is a unit of mass. In science, weight is the force of gravity on a mass, measured in newtons: a 10 kg mass weighs about 98 N on Earth. In everyday speech and trade, “weight” means mass, which is why scales, labels and this page give it in kilograms or pounds. Force units such as the newton, the pound-force and the poundal are left out of the list, so a mass is never converted into a force by mistake.

Grams in a cup? Weight and volume are different

A cup, tablespoon or gallon measures volume, and how much it weighs depends on what fills it, so there is no fixed number of grams in a cup. Water comes close to one rule: the kilogram was first defined as the mass of a liter of water, so 1 mL of water is about 1 g. For flour, sugar or butter, use the weight the recipe gives, or weigh the ingredient; the Volume Converter and the Recipe Scaling Calculator, listed with the related calculators on this page, handle cups, spoons and servings.

Price per pound, per kilogram and per ton

A price per unit converts the other way round from the weight: a kilogram is 2.20462 times heavier than a pound, so a price per kilogram is 2.20462 times the price per pound. Tick Add a price per unit, enter the price, and the converter lists the price per gram, kilogram, metric ton, ounce, pound, short ton, long ton and troy ounce, with the total for your weight. For example, $4.99 per pound is $11.00 per kilogram (4.99 ÷ 0.45359237), and $1,000 per troy ounce is $32.15 per gram (1,000 ÷ 31.1034768).

Reading the result

• The headline is the weight in the To unit, then the equation and whether it is exact or how it was rounded.
• The factor line reads both ways, such as 1 kg ≈ 2.20462262185 lb and 1 lb = 0.45359237 kg exactly: “exactly” marks a defined factor, ≈ a rounded one.
• The three tiles show the weight in related units: stone and pounds and pounds and ounces for body weights, the other two tons when a ton is involved, grams and ounces for small or precious amounts.
• Notes above the steps warn when a conversion involves tons or ounces, where same-named units differ.
• How this was calculated shows the work with your numbers: the exact factor and, for pounds and ounces or stone and pounds, the split into two units.
• The conversion table lists the weight in every unit, grouped as metric, US customary, UK imperial and troy, carat and grain units, each marked Exact or Rounded. Choosing a unit name switches the headline to that unit, and Download CSV or Copy table exports every row.
• The chart lists eleven evenly spaced values of your From unit around your number (1 kg apart around 72.5 kg, 1 oz apart around 7 lb 6 oz) in the To unit; its caption says when every value in it is exact.
• The price table appears when you enter a price, with the total for your weight in its caption.
• Save for comparison keeps up to three conversions side by side, with the change in kilograms from the first.

Common weight conversion mistakes

• Reading 7.6 lb as 7 lb 6 oz. Decimal pounds are not ounces: 7.6 lb is 7 lb 9.6 oz, and 11.4 st is 11 st 5.6 lb, not 11 st 4 lb. The converter points this out when you enter such a number in pounds or stone.
• Mixing up tons. A short ton is 9.3% lighter than a metric ton, and a long ton is 12% heavier than a short ton, so a freight or price figure read in the wrong ton is off by that much.
• Weighing gold in ordinary ounces. 1 troy ounce is 31.1 g, not 28.3 g, about 9.7% more.
• Rounding 0.45359237 or 2.20462 early. Using 2.2 makes 72.5 kg come out 0.335 lb light, and the error grows with the weight.
• Treating fluid ounces or cups as weight. A fluid ounce is a volume; only water weighs close to its volume in grams.

Assumptions and limitations

• The factors are the exact legal definitions in the US and UK, not rounded table values such as 2.2 lb per kilogram; only the final figure on screen is rounded, to the significant figures you pick.
• A converted value can’t be more precise than the scale. A reading of 72.5 kg on a scale that shows 0.1 kg lies between 72.45 and 72.55 kg, which is 159.72 to 159.95 lb, so quoting 159.835140084 lb suggests more certainty than the scale gave.
• Pounds and ounces and stone and pounds round the smaller part once, halves up, before splitting, so they never read 16 oz or 14 lb.
• Weights must be 0 or more and at most 10¹⁵ in the unit typed. Pounds and ounces and stone and pounds go up to 1 trillion lb or 1 trillion stone; choose pounds, stone or tons for anything heavier.
• Units not in the list, such as the hundredweight and the pennyweight, can be converted through pounds or grains, as the questions below show.