A kilogram is the SI base unit for mass. It is used for body weight, shipping, groceries, science, medicine, sports, manufacturing, trade, and nearly every field that needs a standard metric mass unit.
Quick facts
- Unit name
- kilogram
- Plural
- kilograms
- Symbol
- kg
- Quantity
- mass
- System
- International System of Units
- SI role
- base unit for mass
- Gram relation
- 1 kg = 1,000 g
- Pound relation
- 1 kg = 2.2046226218 lb
Visual scale
One kilogram is a practical everyday mass: heavier than a small food portion, close to many packaged grocery items, and light enough to hold in one hand.
Definition and SI role
The kilogram is the SI base unit for mass. In metric conversion, it anchors grams, milligrams, metric tons, and many applied measurements used in science, commerce, health, and engineering.
Symbol and writing rules
The standard symbol is kg. Unit symbols are not pluralized, so write 1 kg and 12 kg, not 12 kgs. In technical writing, put a space between the number and symbol.
Kilogram, mass, and weight
The kilogram is a mass unit, not a force unit. Everyday scales often report body weight or package weight in kilograms, but technically they are reporting mass inferred from force under local gravity. In physics, weight as a force is measured in newtons.
How heavy is one kilogram?
One kilogram is a convenient human-scale unit. It is large enough for groceries, packages, luggage, and body weight, while grams are better for small food portions or lab quantities.
Everyday scale
Many packaged foods, small tools, and household items are naturally described in kilograms.
Body scale
Human body weight in most metric contexts is recorded in kilograms.
Shipping scale
Parcel weight, freight rates, and airline luggage limits often use kilograms.
Metric hierarchy around the kilogram
| Unit | Symbol | Relationship to kilogram | Typical use |
|---|---|---|---|
| milligram | mg | 0.000001 kg | medicine, chemistry, supplements |
| gram | g | 0.001 kg | food, small goods, lab work |
| kilogram | kg | 1 kg | body weight, packages, commerce |
| metric ton | t | 1,000 kg | bulk materials, freight, industry |
Kilogram vs pound
The kilogram is metric and SI. The pound is customary and common in the United States. One kilogram equals about 2.2046226218 pounds, while one pound equals exactly 0.45359237 kilograms.
Common uses
- Body weight, fitness records, medical records, and health tracking.
- Shipping, logistics, luggage limits, and product weights.
- Groceries, packaged goods, agriculture, and commercial trade.
- Science, engineering, manufacturing, and formulas that require SI mass.
How kilograms are measured
Kilograms are measured with scales and balances. Kitchen scales, bathroom scales, postal scales, laboratory balances, and industrial scales all report mass at different precision levels.
- Use a scale with capacity and precision appropriate for the object.
- Tare the container if the container mass should not be included.
- Record the number and unit together, such as 2.5 kg.
Precision and rounding
For everyday use, one or two decimal places may be enough. For shipping, medicine, science, or manufacturing, use the precision required by the scale, label, or specification.
Conversion formulas
Kilogram conversion table
| Kilograms | Grams | Pounds | Ounces | Metric tons |
|---|---|---|---|---|
| 0.1 kg | 100 g | 0.2204622622 lb | 3.527396195 oz | 0.0001 t |
| 1 kg | 1,000 g | 2.204622622 lb | 35.27396195 oz | 0.001 t |
| 5 kg | 5,000 g | 11.02311311 lb | 176.3698097 oz | 0.005 t |
| 10 kg | 10,000 g | 22.04622622 lb | 352.7396195 oz | 0.01 t |
| 100 kg | 100,000 g | 220.4622622 lb | 3,527.396195 oz | 0.1 t |
Common mistakes
- Pluralizing the symbol: write 12 kg, not 12 kgs.
- Using 2.2 as exact: 1 kg is about 2.2046226218 lb.
- Confusing kg and g: 1 kg equals 1,000 g.
- Confusing mass and force: kilogram is mass; newton is force.
- Rounding too early: keep extra digits for shipping, lab, or technical work.
Related Xunits pages
Kilogram converters
Weight references
FAQ
Is the kilogram an SI base unit?
Yes. The kilogram is the SI base unit for mass.
How many grams are in one kilogram?
One kilogram equals exactly 1,000 grams.
How many pounds are in one kilogram?
One kilogram equals about 2.2046226218 pounds.
What is the symbol for kilogram?
The standard symbol is kg.
Is kg weight or mass?
Kilogram is a mass unit. In everyday language, it is often used when people talk about weight.
Should I use kilograms or grams?
Use kilograms for larger everyday masses such as body weight and packages. Use grams for food portions, small goods, and lab quantities.
Is 1 kg exactly 2.2 lb?
No. 2.2 lb is a rough estimate. A more accurate value is 2.2046226218 lb.
Reference notes
This guide treats the kilogram as the SI base unit for mass, uses exact decimal metric relationships, and uses the exact pound relationship of 1 lb = 0.45359237 kg.