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Convert between kilograms, stone, pounds, ounces, grams, and other weight units with this weight conversion tool.
Enter your parameters below to calculate results.
The Weight Conversion tool converts values between metric mass units, avoirdupois units, troy units, and selected commercial mass units. Enter a value in any supported unit to calculate its equivalent in kilograms, grams, pounds, ounces, stones, tons, troy ounces, and other units.
In everyday language, weight is often used to mean mass. Strictly speaking, mass describes the amount of matter in an object, while weight is the force produced by gravity acting on that mass. This converter performs mass-unit conversions. Converting mass to force also requires a specified gravitational acceleration.
Each unit can be expressed using a conversion factor relative to kilograms. To convert from one unit to another:
Target value = Source value × Source factor in kg / Target factor in kg
If the source unit is pounds and the target is kilograms, use the exact international pound definition:
10 lb × 0.45359237 kg/lb = 4.5359237 kg
To convert the result back to pounds, divide by 0.45359237:
4.5359237 kg / 0.45359237 kg/lb = 10 lb
| Quantity | Meaning | SI Unit |
|---|---|---|
| Mass | An object's inertial property or amount of matter. | Kilogram, kg |
| Weight | The force exerted on an object by gravity. | Newton, N |
Weight force is calculated using:
W = m × g
Here W is force in newtons, m is mass in kilograms, and g is gravitational acceleration in meters per second squared. Using standard gravity, gn = 9.80665 m/s2, a mass of 1 kg corresponds to a weight force of 9.80665 N. Actual local gravity varies with location.
The kilogram, symbol kg, is the SI base unit of mass. Metric prefixes create larger and smaller units in powers of ten.
| Unit | Symbol | Equivalent in Kilograms | Equivalent in Grams |
|---|---|---|---|
| Metric tonne | t | 1000 kg | 1000000 g |
| Kilogram | kg | 1 kg | 1000 g |
| Hectogram | hg | 0.1 kg | 100 g |
| Dekagram | dag | 0.01 kg | 10 g |
| Gram | g | 0.001 kg | 1 g |
| Decigram | dg | 0.0001 kg | 0.1 g |
| Centigram | cg | 0.00001 kg | 0.01 g |
| Milligram | mg | 0.000001 kg |
SI symbols are case-sensitive. The correct symbol for kilogram is kg, not Kg, and the symbol for milligram is mg, not MG.
The avoirdupois system is used for most everyday goods in the United States and for common pound and ounce measurements. One avoirdupois pound contains 16 avoirdupois ounces or 7000 grains.
| Unit | Symbol | Equivalent Mass |
|---|---|---|
| Short ton | short ton | 2000 lb = 907.18474 kg |
| Short hundredweight | cwt | 100 lb = 45.359237 kg |
| Stone | st | 14 lb = 6.35029318 kg |
| Pound | lb | 0.45359237 kg |
| Avoirdupois ounce | oz | 28.349523125 g |
| Avoirdupois dram | dr | 1.7718451953125 g |
| Grain | gr | 64.79891 mg |
| Unit | Pounds | Kilograms |
|---|---|---|
| Long hundredweight | 112 lb | 50.80234544 kg |
| Long ton | 2240 lb | 1016.0469088 kg |
The words ton and hundredweight are ambiguous unless the system is stated. A metric tonne, U.S. short ton, and Imperial long ton are three different masses.
Troy units are commonly used for precious metals. A troy ounce is heavier than an avoirdupois ounce, but a troy pound is lighter than an avoirdupois pound because the troy pound contains only 12 troy ounces.
| Troy Unit | Symbol | Equivalent Mass |
|---|---|---|
| Troy pound | lb t | 12 oz t = 373.2417216 g |
| Troy ounce | oz t | 480 gr = 31.1034768 g |
| Pennyweight | dwt | 24 gr = 1.55517384 g |
| Grain | gr | 64.79891 mg |
The grain has the same mass in the avoirdupois, troy, and apothecaries systems. The systems differ in the number of grains in an ounce or pound.
| Unit | Grains | Grams | Typical Use |
|---|---|---|---|
| Avoirdupois ounce | 437.5 gr | 28.349523125 g | Everyday goods and general commerce |
| Troy ounce | 480 gr | 31.1034768 g | Precious metals |
One troy ounce is approximately 9.7% heavier than one avoirdupois ounce. Always include the word troy or the symbol oz t when the distinction matters.
| Unit | Symbol | Equivalent Mass | Typical Use |
|---|---|---|---|
| Metric carat | ct | 200 mg = 0.2 g | Gemstone mass |
| Grain | gr | 64.79891 mg | Small masses and selected industries |
| Pennyweight | dwt | 1.55517384 g | Precious metals and jewelry |
Do not confuse carat, a unit of gemstone mass, with karat, a measure of gold purity.
The original page included the following mass-unit reference image. It has been retained for comparison with the calculator fields.
Convert 150 lb to kilograms:
150 × 0.45359237 = 68.0388555 kg
Convert 2.5 kg to pounds:
2.5 / 0.45359237 = 5.51156 lb
Convert 10 troy ounces to grams:
10 × 31.1034768 = 311.034768 g
Convert 5 stone to kilograms:
5 × 6.35029318 = 31.7514659 kg
Convert 750 g to ounces:
750 / 28.349523125 = 26.4555 oz
| Unit | Kilograms | Pounds |
|---|---|---|
| Metric tonne | 1000 kg | 2204.62262 lb |
| U.S. short ton | 907.18474 kg | 2000 lb |
| Imperial long ton | 1016.0469088 kg | 2240 lb |
Write tonne, short ton, or long ton rather than ton alone when the context could be international.
An exact conversion factor does not make the input measurement exact. A value measured as 10 lb should not automatically be reported with many decimal places simply because the calculator can display them. Keep sufficient digits during the calculation, then round the final value to match the measurement uncertainty and purpose.
Commercial scales, laboratory balances, kitchen scales, and industrial weighing systems have different readability, capacity, calibration, and uncertainty. The converter changes units; it does not improve the accuracy of the original measurement.
Volume cannot be converted directly to mass unless the material density is known. The relationship is:
Mass = Density × Volume
Density may change with temperature, pressure, composition, and concentration. This is why one cup of water and one cup of oil do not necessarily have the same mass, even though their volumes are equal.
The kilogram, symbol kg, is the SI base unit of mass.
Mass is an intrinsic property measured in kilograms. Weight is a force caused by gravity and is measured in newtons.
One international avoirdupois pound equals exactly 0.45359237 kg.
One avoirdupois ounce equals 28.349523125 g. One troy ounce equals 31.1034768 g, so the unit system must be specified.
One stone equals 14 avoirdupois pounds.
No. A metric tonne is 1000 kg, while a U.S. short ton is 907.18474 kg.
No. A troy pound is 373.2417216 g, while an avoirdupois pound is 453.59237 g. The troy ounce is heavier, but the troy pound contains only 12 troy ounces.
Only after specifying the gravitational acceleration. Under standard gravity, multiply kilograms by 9.80665 to obtain weight force in newtons.
Not without knowing the density. For water under ordinary conditions, the numerical values may be similar, but that shortcut does not apply to all materials or precision work.
| 0.001 g |
| Microgram | µg | 0.000000001 kg | 0.000001 g |
| Nanogram | ng | 0.000000000001 kg | 0.000000001 g |
| Picogram | pg | 0.000000000000001 kg | 0.000000000001 g |