How to use the weight converter
Select the unit you are starting with, enter a value, choose the unit you need, and press Calculate. The converter shows the result along with equivalent values in other supported units. Use the Swap button to reverse the conversion direction.
This tool is useful when following recipes, checking luggage limits, comparing package weights, reading product specifications, or converting body-weight measurements. For related measurements, see our length converter, volume tool, and temperature converter.
Weight and mass: what is the difference?
In everyday conversation, people often use “weight” and “mass” interchangeably. In physics, they describe different concepts. Mass measures how much matter an object contains, while weight is the force gravity exerts on that mass. Mass is commonly measured in kilograms and grams, while force is measured in newtons.
The units in this converter are mass units used for ordinary measurements. Converting between them changes the numerical representation of the same mass; it does not change the object itself.
Weight conversion formula
The converter uses kilograms as its common reference unit. Each supported unit has a fixed conversion factor to kilograms. To convert a value, first multiply it by the source unit’s factor, then divide by the target unit’s factor.
One pound equals exactly 0.45359237 kilograms. To convert pounds to kilograms, multiply the number of pounds by 0.45359237. To convert kilograms to pounds, divide by 0.45359237, or multiply by approximately 2.20462262.
Weight conversion reference table
These standard relationships are useful for checking common conversions. Values marked as approximate are rounded for convenient everyday use.
| Unit | Equivalent | Common use |
|---|---|---|
| 1 milligram (mg) | 0.001 grams | Very small masses |
| 1 gram (g) | 0.001 kilograms | Food and small objects |
| 1 kilogram (kg) | 1,000 grams | Everyday metric measurements |
| 1 kilogram (kg) | Approximately 2.20462 pounds | Metric-to-US conversion |
| 1 pound (lb) | Exactly 0.45359237 kilograms | US customary measurements |
| 1 pound (lb) | 16 ounces | Food and parcel weights |
| 1 stone (st) | 14 pounds | UK body-weight measurements |
| 1 metric tonne (t) | 1,000 kilograms | Industrial and freight loads |
| 1 US short ton | 2,000 pounds | US bulk materials and freight |
A metric tonne and a US short ton are different units. A metric tonne is 1,000 kilograms, while a US short ton is 2,000 pounds. For shipping or commercial transactions, confirm which definition is specified.
Metric vs. US customary weight units
Metric system
The metric system is based on powers of ten. Moving between milligrams, grams, kilograms, and metric tonnes involves multiplying or dividing by 1,000 at each step.
US customary and UK units
Customary units use different relationships. There are 16 ounces in a pound, 14 pounds in a stone, and 2,000 pounds in a US short ton.
If a label gives a value in pounds but your scale displays kilograms, convert the value before comparing them. Explore more tools in the Converters category.
Worked weight conversion examples
Kilograms to pounds
Convert 5 kg to pounds.
Grams to ounces
Convert 250 g to ounces.
Stones to kilograms
Convert 10 stone to kilograms.
Choosing the right unit for the task
The most convenient unit depends on the size of the object and the measurement system being used. Milligrams and grams are practical for small quantities; kilograms and pounds suit many everyday measurements; metric tonnes and US short tons are better suited to heavy loads.
| Situation | Common unit | Why it helps |
|---|---|---|
| Small recipe quantities | Grams or ounces | Convenient for portions and ingredients |
| Body-weight records | Kilograms, pounds, or stones | Matches the scale or reporting convention |
| Parcel and luggage checks | Kilograms or pounds | Helps compare an item with a stated limit |
| Industrial materials | Metric tonnes or US short tons | Represents large quantities more conveniently |
For parcels, luggage, and commercial goods, conversion alone does not determine whether an item meets a carrier’s limit. Check the applicable rules and rounding policy before making a final decision.
Accuracy, significant digits, and rounding
A calculator can display many decimal places, but that does not mean the original measurement was that precise. If a kitchen scale reads 250 grams, reporting a converted value to ten decimal places may suggest more certainty than the measurement supports.
Use two decimal places for quick everyday comparisons, four to six for more detailed conversions, and additional digits only when needed. The converter uses standard conversion factors and rounds the displayed result according to your selected precision.
Frequently asked questions
How many pounds are in one kilogram?
One kilogram is approximately 2.20462262 pounds. For many everyday uses, 1 kg ≈ 2.2 lb is a convenient approximation.
How many kilograms are in one pound?
One international avoirdupois pound is exactly 0.45359237 kilograms. Multiply pounds by this factor to obtain kilograms.
How many ounces are in a pound?
There are 16 ounces in one pound in the common avoirdupois system used for everyday US weight measurements.
How many pounds are in a stone?
One stone equals 14 pounds. The stone is commonly used for human body weight in the United Kingdom.
What is the difference between a metric tonne and a US short ton?
A metric tonne equals 1,000 kilograms. A US short ton equals 2,000 pounds, or approximately 907.18474 kilograms. They are different units and should not be substituted without conversion.
Can I convert a decimal or fractional value?
Yes. Enter decimal values such as 2.5 kg or 0.75 lb. The calculator accepts non-negative decimal inputs.
Why does the answer change when I choose more decimal places?
The underlying conversion factor remains the same, but the displayed result is rounded to the number of decimal places you select. More digits reveal more of the calculated value.
Does converting weight change an object's mass?
No. A unit conversion changes how a measurement is expressed, not the measured mass. In physics, mass and weight are distinct: weight is the force caused by gravity.
Which unit should I use for shipping?
Use the unit requested by the carrier or shipping service. Convert between kilograms and pounds when needed, and check the carrier's rounding rules and maximum-weight requirements.