Weight Converter

How this weight conversion is calculated

Every unit is a number of grams. The result is amount × (grams in the "from" unit) ÷ (grams in the "to" unit), rounded to six decimal places. The pound in the code is the international avoirdupois pound, exactly 0.45359237 kilograms, which is 453.59237 grams. That is the 1959 yard-and-pound definition NIST uses in Special Publication 811. The ounce is that pound divided by 16, 28.349523125 grams. The stone is 14 of those pounds, 6350.29318 grams. The US ton (short) is 2,000 pounds, 907184.74 grams. The UK ton (long) is 2,240 pounds, 1016046.9088 grams. The metric ton is 1,000 kilograms, 1,000,000 grams. Milligrams and kilograms are exact powers of ten from the gram.

The labels say weight because that is what packages and forms say. The factors are masses. The page does not convert newtons, and it does not change the result for a different planet. There is no troy ounce. Precious-metal weights use a different ounce. If you pick the ounce in this list, you get the avoirdupois ounce of 28.349523125 grams, which is the kitchen and shipping ounce, not the troy ounce. NIST's conversion tables are the place to look up the troy ounce. It is not a menu entry here. There is also no fluid ounce. A fluid ounce is a volume.

Worked examples

Example 1: 150 pounds to kilograms

150 × 453.59237 ÷ 1000 = 68.0388555 kilograms, which displays as 68.038856. One pound in the other direction displays as 0.453592 kilograms. The definition is 0.45359237 kilograms. The last two digits are hidden by the six-decimal rounding of a one-pound result. The factor used in the multiplication is still the full 453.59237 grams. One kilogram displays as 2.204623 pounds.

Example 2: Ounces, and sixteen of them

1 ounce displays as 28.349523 grams. 8 ounces display as 226.796185 grams. 16 ounces to pounds displays as 1, because the ounce factor is exactly one sixteenth of the pound factor. If 16 ounces does not come back as 1 pound, the ounce you selected is not this one. A fluid ounce will not, because it is not in this menu at all.

Example 3: Stone, short ton, long ton, metric ton

11 stone displays as 154 pounds, because a stone is exactly 14 pounds and 11 × 14 = 154. The form has one amount. It will not read "11 stone 4 pounds" as a mixed string. Convert 11 stone to 154 pounds, add the 4 yourself, and convert 158 pounds in a second pass if that is the body weight you were given. 1 US short ton displays as 2000 pounds and as 0.907185 metric tons. 1 UK long ton displays as 2240 pounds. 1 metric ton displays as 2204.622622 pounds. A freight quote that says "ton" without short, long, or metric is not finished. The three menu rows are three sizes.

When to use this

Use it when two numbers are the same kind of mass and the units differ: a scale in pounds and a form in kilograms, a package in ounces and a price list in grams, a UK weight in stone and a US form in pounds. After both package sizes are in one unit, the Unit Price Calculator divides price by size. It does not convert the size for you. A cup of flour is not a mass until you pick an ingredient. That is the Cooking Measurement Converter. Body mass index is not computed here. The BMI Calculator has its own imperial path, pounds and inches with a 703 factor, and a metric path in kilograms and centimeters. If you convert pounds to kilograms on this page and then use the BMI metric mode, the last decimal can differ from typing the pounds into the BMI imperial mode, because 703 is a rounded stand-in for the exact pound and inch definitions. For the BMI page's own number, type the units that page asks for.

Seventy kilograms, and what this page will not add

70 kilograms displays as 154.323584 pounds. That is a single conversion. It is not a BMI, and it is not a body-fat estimate. The body fat percentage tool wants tape measurements in inches, not a converted scale weight. Stone-and-pounds notation is two numbers. This field is one number. Do the addition in pounds, then convert once. Shipping rates that use dimensional weight are the carrier's rule. This page converts the mass you typed. It does not compare it with a volumetric weight.

Common mistakes

• Picking the ounce for a fluid ounce. This ounce is 28.349523125 grams of mass. Volume fluid ounces are on the volume converter. They are a different quantity.
• Using this ounce for gold or silver. Bullion is weighed in troy ounces. This menu's ounce is avoirdupois. The page will not warn you, because both are called ounces on labels.
• Treating short ton, long ton, and tonne as synonyms. They display as 2000 pounds, 2240 pounds, and 2204.622622 pounds.
• Typing 11 stone 4 pounds into one box. Convert 11 stone (154 pounds), add 4, then convert 158 pounds. The box does not parse a mixed weight.
• Rounding 1 pound to 0.45 kg and then scaling. 150 pounds displays as 68.038856 kg. 150 × 0.45 = 67.5, which is a different number.
• Converting into BMI twice. The BMI imperial mode already contains a pound-based formula. Converting to kilograms and also using the imperial BMI path double-converts.

Limitations

Nine mass units, grams as the only base, six decimal places on output. No troy ounce, no fluid ounce, no carat, no grain, no newton, no tare, and no density. A gram of water is not assumed to be a milliliter. Jewelry, postage, and pharmacy systems that use other units need those units. The international pound is a definition and does not drift. A bathroom scale's rounding is the scale's, and this page converts the number you type, not the number the scale might have rounded before you read it.

Eight ounces, and the one-pound display

Eight ounces display as 226.796185 grams. Sixteen display as 1 pound, with nothing left over, because the ounce factor is the pound divided by 16. The other direction is where rounding shows: 1 pound displays as 0.453592 kilograms, while the factor in the code is 0.45359237 kilograms. The last digits are hidden by the six-decimal result, not replaced by a different pound. When you check the page by hand, multiply by 453.59237 grams and only then round to six decimals.

FAQ

Is 1 pound exactly 0.45359237 kilograms?

Yes. That is the factor in the code, the international avoirdupois pound. The panel shows a one-pound result as 0.453592 kilograms because it rounds to six decimal places. 150 pounds displays as 68.038856 kilograms, from the full factor.

Why is 16 ounces exactly 1 pound here?

The ounce factor is the pound factor divided by 16. Sixteen ounces displays as 1 pound. One ounce displays as 28.349523 grams.

What is a stone on this page?

Exactly 14 international pounds. Eleven stone displays as 154 pounds. A mixed "11 stone 4 pounds" has to be added in pounds first. The field holds one number.

Which ton is 2,000 pounds?

The US ton (short). The UK ton (long) displays as 2240 pounds. The metric ton displays as 2204.622622 pounds and as 1000 kilograms. One short ton displays as 0.907185 metric tons.

Can I use this for a body weight before BMI?

You can convert the mass. BMI is calculated on the BMI page. Its imperial mode uses a 703 factor rather than calling this converter, so the last decimal can differ if you convert here and then switch BMI modes.

Does this include the troy ounce?

No. The ounce in the list is the avoirdupois ounce of 28.349523125 grams. Troy weights used for precious metals are a different unit. NIST's conversion tables define it. This menu does not.

Why does a kitchen scale disagree by a gram?

This page converts the number you type and then rounds to six decimal places. A kitchen scale that displays whole grams has already rounded. Convert the scale's displayed number. Do not expect the page to recover digits the scale never showed.

Related calculators

• Volume Converter for fluid ounces and gallons
• Unit Price Calculator
• BMI Calculator
• Cooking Measurement Converter when the question is grams of a cup of flour
• Cooking measurement myths on why a cup of flour is not one weight
• Length Converter