Weight and Mass Converter
Convert weight and mass between kilograms, grams, pounds, ounces, stone, tons and many other units. Choose two units, enter a value and read the result.
Select two units to see the conversion factor.
This tool converts mass (the amount of matter). It does not convert force. Pound-force, kilogram-force and the poundal are force units and are not included.
Weight and Mass Formula
Every mass unit is a fixed part of the kilogram. Result = value × (size of source unit in kg ÷ size of target unit in kg). The key sizes are exact: 1 pound = 0.45359237 kg, 1 ounce = 1/16 pound, 1 grain = 1/7000 pound, and 1 carat = 0.2 g. A short ton is 2,000 pounds and a long ton is 2,240 pounds.
What Is Mass, and How Is It Different from Weight?
Mass is how much matter an object contains. It does not change from place to place. The SI unit is the kilogram (kg). Weight in science is the force of gravity on that mass, and it is measured in newtons. In daily life people say “weight” when they mean mass, and shop scales show mass in kilograms or pounds. That is how this tool uses the word.
Pound-mass is not pound-force. A pound (lb) here is a unit of mass, exactly 0.45359237 kg. A pound-force is a unit of force, about 4.448 newtons. The two are not interchangeable, so force units are left out of this converter.
The units come in four groups. Metric: gram, kilogram, tonne, quintal and the prefixes from attogram to exagram. Avoirdupois (everyday US and UK): ounce, pound, stone, hundredweight, quarter and the short and long ton. Troy and apothecary: troy ounce and pound, pennyweight and scruple, used for precious metals and old pharmacy. Scientific: atomic mass unit, dalton, particle masses, and the masses of the Earth and Sun.
US and UK units differ. A US hundredweight is 100 lb but a UK hundredweight is 112 lb. A US ton is 2,000 lb, a UK ton is 2,240 lb and a metric tonne is 1,000 kg. They are labelled clearly so you can pick the right one.
Supported Units
This converter supports the following 52 mass units. The last column gives the size of each unit in kilograms.
| Unit | Symbol | Value in kg |
|---|---|---|
| Kilogram | kg | 1 |
| Gram | g | 0.001 |
| Exagram | Eg | 1e+15 |
| Petagram | Pg | 1e+12 |
| Teragram | Tg | 1,000,000,000 |
| Gigagram | Gg | 1,000,000 |
| Megagram | Mg | 1,000 |
| Hectogram | hg | 0.1 |
| Dekagram | dag | 0.01 |
| Decigram | dg | 0.0001 |
| Centigram | cg | 1e-5 |
| Milligram | mg | 1e-6 |
| Microgram | µg | 1e-9 |
| Nanogram | ng | 1e-12 |
| Picogram | pg | 1e-15 |
| Femtogram | fg | 1e-18 |
| Attogram | ag | 1e-21 |
| Tonne (metric ton) | t | 1,000 |
| Kiloton (metric) | kt | 1,000,000 |
| Quintal (metric) | q | 100 |
| Carat (metric) | ct | 0.0002 |
| Gamma | γ | 1e-9 |
| Pound (avoirdupois) | lb | 0.45359237 |
| Ounce (avoirdupois) | oz | 0.02834952313 |
| Dram (avoirdupois) | dr | 0.001771845195 |
| Grain | gr | 6.479891e-5 |
| Stone (14 lb) | st | 6.35029318 |
| Quarter (US, 25 lb) | qr (US) | 11.33980925 |
| Quarter (UK, 28 lb) | qr (UK) | 12.70058636 |
| Hundredweight (US, 100 lb) | cwt (US) | 45.359237 |
| Hundredweight (UK, 112 lb) | cwt (UK) | 50.80234544 |
| Ton (short, US, 2000 lb) | ton (US) | 907.18474 |
| Ton (long, UK, 2240 lb) | ton (UK) | 1,016.046909 |
| Kilopound (kip) | kip | 453.59237 |
| Pound (troy or apothecary) | lb t | 0.3732417216 |
| Ounce (troy or apothecary) | oz t | 0.0311034768 |
| Pennyweight | pwt | 0.00155517384 |
| Scruple (apothecary) | s ap | 0.0012959782 |
| Ton (assay, US) | AT (US) | 0.02916666667 |
| Ton (assay, UK) | AT (UK) | 0.03266666667 |
| Slug (lbf·s²/ft) | slug | 14.59390294 |
| Kilogram-force second squared per meter (hyl) | kgf·s²/m | 9.80665 |
| Atomic mass unit | u | 1.660539069e-27 |
| Dalton | Da | 1.660539069e-27 |
| Planck mass | mP | 2.176434e-8 |
| Electron mass (rest) | mₑ | 9.109383714e-31 |
| Muon mass | m_μ | 1.883531627e-28 |
| Proton mass | mₚ | 1.672621926e-27 |
| Neutron mass | mₙ | 1.674927501e-27 |
| Deuteron mass | m_d | 3.343583777e-27 |
| Earth’s mass (IAU nominal) | M⊕ | 5.9722e+24 |
| Sun’s mass (IAU nominal) | M☉ | 1.98841e+30 |
How to Use the Weight and Mass Converter
- Type the mass in the value box. Decimals and scientific notation such as 0.0025 or 2.5e-3 are accepted.
- Choose the From unit and the To unit.
- The result appears instantly, or press Convert Now. Very large or very small results are shown in scientific notation.
- Use Swap Units to reverse the conversion, Copy Result to copy the answer, open Show this value in all units for a full list, and Clear to start again.
Step-by-step by hand
- Find the size of each unit in the common base unit (kg): 1 kg = 1 kg and 1 lb = 0.45359237 kg.
- Divide the source size by the target size to get the conversion factor: 1 ÷ 0.45359237 = 2.204622622, so 1 kg = 2.204622622 lb.
- Multiply by your value: 70 kg × 2.204622622 = 154.3235835 lb.
Mass cannot be negative, so enter zero or a positive number.
Common Weight and Mass Conversions
- Body weight: 70 kg equals 154.3235835 lb and 11.02311311 stone.
- Cooking: 250 g equals 8.818490487 oz.
- Luggage: 23 kg equals 50.7063203 lb.
- Gold: 1 troy ounce equals 31.1034768 g, which is more than a normal ounce (28.34952313 g).
- Gemstones: 5 carats equals 1 g.
- Freight: 1 short ton equals 907.18474 kg; 1 long ton equals 1,016.046909 kg.
- Grain mill: 1 quintal equals 100 kg.
Kilogram to Other Mass Units
Quick reference for frequently used values
| kg | lb | oz | st |
|---|---|---|---|
| 0.5 | 1.102311311 | 17.63698097 | 0.07873652221 |
| 1 | 2.204622622 | 35.27396195 | 0.1574730444 |
| 5 | 11.02311311 | 176.3698097 | 0.7873652221 |
| 10 | 22.04622622 | 352.7396195 | 1.574730444 |
| 25 | 55.11556555 | 881.8490487 | 3.93682611 |
| 50 | 110.2311311 | 1,763.698097 | 7.873652221 |
| 75 | 165.3466966 | 2,645.547146 | 11.81047833 |
| 100 | 220.4622622 | 3,527.396195 | 15.74730444 |
Where and Why This Conversion Is Used
- Health and fitness: body weight in kg, lb or stone.
- Cooking and shopping: grams and ounces on recipes and packaging.
- Travel and shipping: baggage limits and freight loads in kg, lb and tons.
- Jewelry and trade: carats, troy ounces and pennyweights.
- Farming: quintals and tonnes for crops.
- Science: atomic mass unit and particle masses.
Important Limitations
- The tool converts mass to mass only. It cannot convert volume to mass, because that needs the density of the material.
- It does not convert force. A weight in newtons or pound-force is a different quantity.
- Particle, planet and star masses are measured values and may be refined over time.
- Biblical, Greek and Roman units (talent, mina, shekel and others) are left out. Their true size is uncertain and differs between sources.