On this page
Formula
Target value = Value × (Kilograms per source unit ÷ Kilograms per target unit)
- Value
- the weight you type in
- Kilograms per unit
- the exact size of each unit in kilograms (1 lb = 0.45359237 kg, 1 oz = 0.028349523125 kg, 1 st = 6.35029318 kg)
- Target value
- the same mass in the unit you convert to
What the weight converter covers
This weight converter changes a mass from one unit to any other in the metric and US customary systems. It also works as a mass converter, since everyday scales report mass in the same units. Enter a number, pick the unit it is in and the unit you want, and the result appears with the exact multiplier. The table under the result lists the same amount in every unit, from milligrams to tons.
The units fall into three groups:
- Metric: milligram, gram, kilogram and metric ton, each 1,000 times the one before.
- US customary (avoirdupois): ounce, pound and short ton. 16 ounces make a pound and 2,000 pounds make a ton.
- Stone: 14 pounds, still common for body weight in the UK and Ireland.
How to use the weight converter
- Type the amount in the Value box. Decimals and thousands separators such as 1,250 are fine.
- Choose the unit you are starting from in From, for example pounds.
- Choose the unit you need in To, for example kilograms. The answer updates as you type.
- Check the working line for the exact factor, and scan the table for the same weight in every other unit.
- Use Copy result to paste the conversion as a sentence, or Share to send a link that reopens the converter with your numbers.
To swap direction, just exchange the two units; there is no separate reverse tool to find.
Weight converter formula: converting by hand
Every unit is a fixed number of kilograms, so any conversion is one multiplication and one division. The key link between the systems is the pound: since 1959 it has been exactly 0.45359237 kg.
Say a suitcase weighs 21 kg and you want pounds:
- Kilograms per pound: 0.45359237.
- 21 ÷ 0.45359237 = 46.297 lb.
- For ounces, take the 0.297 lb remainder and multiply by 16: 4.75 oz. The case weighs about 46 lb 5 oz.
Ounces to grams works the same way. A 6 oz chicken breast is 6 × 28.3495 = 170.1 g.
Weight conversion chart
The exact definitions behind every result, with each unit expressed in grams, pounds and kilograms. Figures are calculated with the converter’s own factors.
| Unit | In grams | In pounds | In kilograms |
|---|---|---|---|
| 1 milligram | 0.001 | 0.0000022 | 0.000001 |
| 1 gram | 1 | 0.0022046 | 0.001 |
| 1 ounce | 28.349523 | 0.0625 | 0.0283495 |
| 1 pound | 453.59237 | 1 | 0.4535924 |
| 1 kilogram | 1,000 | 2.2046226 | 1 |
| 1 stone | 6,350.29318 | 14 | 6.3502932 |
| 1 US ton | 907,184.74 | 2,000 | 907.18474 |
| 1 metric ton | 1,000,000 | 2,204.6226 | 1,000 |
Quick reference for common conversions
| From | To | Multiply by | Example |
|---|---|---|---|
| Pounds | Kilograms | 0.45359237 | 5 lb = 2.268 kg |
| Kilograms | Pounds | 2.2046226 | 2 kg = 4.409 lb |
| Ounces | Grams | 28.349523 | 4 oz = 113.4 g |
| Grams | Ounces | 0.035274 | 500 g = 17.637 oz |
| Stone | Pounds | 14 | 9 st = 126 lb |
| Metric tons | US tons | 1.1023113 | 10 t = 11.023 ton |
Where these conversions come up
- Cooking: US recipes give weights in ounces and pounds, while most of the world uses grams. Kitchen scales often switch between them, but a converter helps with package sizes and scaling. For recipes measured in cups, see the cups to grams converter, and for liquids the volume converter.
- Body weight: doctors’ offices in the US record pounds, many fitness apps use kilograms, and UK friends talk in stone. The kg to lbs converter splits a result into pounds and ounces or stone and pounds.
- Shipping and travel: couriers price parcels by the pound or kilogram, and baggage allowances are usually set in kilograms with a pound equivalent.
- Building and freight: bulk materials, trucks and cargo are rated in tons, so knowing whether a quote means metric or short tons avoids a 10% surprise.
Common mistakes
- Mixing fluid ounces and ounces. A fluid ounce is a volume, an ounce is a weight. 8 fl oz of water weighs about 8.3 oz, but 8 fl oz of honey weighs much more.
- Assuming a ton is a ton. Metric, short and long tons are 1,000 kg, 907 kg and 1,016 kg. Check which one a document means.
- Using 2.2 for precise work. Multiplying kilograms by 2.2 instead of 2.20462 understates pounds by about 0.2%, which adds up on large shipments.
- Reading stone like decimal pounds. 10.5 st is 10 st 7 lb, not 10 st 5 lb.
- Comparing gold prices with a kitchen scale. Precious metals are priced in troy ounces of about 31.1 g, roughly 10% heavier than the avoirdupois ounce used here.
Glossary
- Avoirdupois: the system of pounds and ounces used for everyday goods in the US.
- Tonne: another name for the metric ton of 1,000 kg.
- Short ton: the US ton of 2,000 lb. The British long ton is 2,240 lb.
Worked examples
Body weight in kilograms
Convert a body weight of 150 pounds to kilograms.
Inputs: Value = 150; From = Pounds (lb); To = Kilograms (kg)
150 lb × 0.45359237 = 68.038856 kg
Answer: 150 lb = 68.038856 kg
Ounces to grams for a recipe
A package holds 12 ounces. How many grams is that?
Inputs: Value = 12; From = Ounces (oz); To = Grams (g)
12 oz × 28.349523125 = 340.194278 g
Answer: 12 oz = 340.194278 g
Stone to pounds
A UK weight of 11 stone, in pounds.
Inputs: Value = 11; From = Stones (st); To = Pounds (lb)
11 st × 14 = 154 lb
Answer: 11 st = 154 lb
Metric tons vs US tons (edge case)
A 2.5 metric ton load expressed in US short tons, which are about 10% lighter.
Inputs: Value = 2.5; From = Metric tons (t); To = US tons (short) (ton)
2.5 t × 1.1023113109 = 2.755778 ton
Answer: 2.5 t = 2.755778 ton
Assumptions and limitations
- Pounds and ounces are avoirdupois units, the everyday system for body weight, food and shipping. 1 lb = 0.45359237 kg exactly, and 16 oz = 1 lb.
- A stone is 14 lb. A US ton (short ton) is 2,000 lb; a metric ton (tonne) is 1,000 kg. The British long ton of 2,240 lb is not included.
- Troy ounces (used for precious metals) and grains are not included in this version; a troy ounce is about 31.1 g, heavier than an ordinary ounce.
- The converter treats weight and mass as the same quantity, as scales and food labels do. It doesn't convert to force units such as newtons.
- Results show up to 6 decimal places and values can't be negative.
Frequently asked questions
Is weight the same as mass?
Strictly, no. Mass is the amount of matter and doesn't change; weight is the force gravity puts on that mass. On Earth, scales are calibrated so the two read the same, which is why kilograms and pounds are used for both in everyday life.
How many grams are in an ounce?
One ounce is 28.349523125 grams exactly, usually rounded to 28.35 g. A 1.5 oz portion of cheese is 1.5 × 28.35 = 42.5 g, and 500 g is about 17.6 oz.
How many pounds are in a stone?
A stone is exactly 14 pounds, or 6.35 kg. It is still used for body weight in the UK and Ireland, so 13 st 4 lb is 13 × 14 + 4 = 186 lb.
What is the difference between a metric ton and a US ton?
A metric ton (tonne) is 1,000 kg, about 2,204.6 lb. A US short ton is 2,000 lb, or 907.18 kg. The metric ton is about 10% heavier, which matters when comparing freight, gravel or vehicle ratings.
How do you convert pounds to kilograms in your head?
Halve the pounds and take off 10% of that half. For 140 lb, half is 70 and 10% of 70 is 7, giving 63 kg. The exact answer is 63.5 kg, so the shortcut is within 1%.
Can I convert cups to grams with a weight converter?
Not directly. Cups measure volume, so the grams depend on what is in the cup. A cup of flour weighs far less than a cup of sugar. Use the [cups to grams converter](/cups-to-grams/), which uses ingredient densities.
Sources
- SI Units - Mass — National Institute of Standards and Technology (NIST). Checked October 12, 2026.
- NIST Guide to the SI, Appendix B.8: Factors for Units Listed Alphabetically — National Institute of Standards and Technology (NIST). Checked October 12, 2026.
- Unit Conversion — National Institute of Standards and Technology (NIST). Checked October 12, 2026.