Weight and mass converter guide
In everyday language, “weight” often refers to mass in kilograms or pounds. Scientifically, mass and weight are different: kilogram and pound are mass units, while newton and pound-force measure force.
This converter performs mass conversion through kilograms. The avoirdupois pound is exactly 0.45359237 kg; ounces, grains, stones, short tons, and long tons are derived from that defined pound.
How to convert weight and mass units
- Enter the mass: Provide a finite, non-negative amount.
- Choose the source: Select the exact metric, avoirdupois, ton, grain, or carat unit.
- Choose the target: Select the output unit or use Swap.
- Convert: Select Convert mass to calculate through kilograms.
Formula and variables
Each supported mass is converted to kilograms and then to the target unit.
target mass = source mass × (kilograms per source unit) ÷ (kilograms per target unit)- mₛ — Source mass
- A finite, non-negative quantity of matter.
- fₛ — Source factor
- Kilograms represented by one source unit.
- fₜ — Target factor
- Kilograms represented by one target unit.
Convert kilograms to pounds
Express 1 kg as avoirdupois pounds.
- Amount
- 1
- From
- kg
- To
- lb
- 1 kg ÷ 0.45359237 kg/lb
Result: 1 kg ≈ 2.20462262185 lb.
This is a mass conversion; it does not calculate gravitational force.
Understanding your results
Mass versus weight force
kg, lb, oz, stone, and tonnes are treated as mass units here. Use a force converter for N, lbf, or kgf.
Ton conventions
A tonne is 1000 kg, a US short ton is 2000 lb, and a UK long ton is 2240 lb. Keep the qualifier.
Assumptions
- One avoirdupois pound is exactly 0.45359237 kg.
- One avoirdupois ounce is 1/16 lb and one grain is 1/7000 lb.
- One stone is 14 lb.
- One metric carat is exactly 0.2 g.
Limitations
- The calculator does not calculate gravitational force.
- Troy ounces and apothecaries units are not included.
- Local gravity is irrelevant to this mass-only conversion.
- The input measurement determines practical precision.
Common mistakes
- Treating kilograms as a force unit.
- Confusing avoirdupois and troy ounces.
- Writing ton without US, UK, or metric qualification.
- Using rounded pound factors in precision work.
- Assuming mass changes when local gravity changes.
Practical use cases
Personal and shipping mass
Compare kg, lb, oz, stone, tonnes, and customary ton conventions.
Small masses
Convert micrograms, milligrams, grams, grains, and metric carats with explicit units.
Planning and decision guide
Name the ton and ounce system
Always record tonne, US short ton, UK long ton, avoirdupois ounce, or another applicable convention. An unqualified label can be materially ambiguous.
Frequently asked questions
How many pounds are in one kilogram?
One kilogram is approximately 2.20462262185 avoirdupois pounds.
Is kilogram a unit of weight or mass?
Kilogram is the SI base unit of mass. Everyday speech often calls a mass value “weight.”
How many kilograms are in one pound?
One avoirdupois pound is exactly 0.45359237 kg.
Are all tons the same?
No. A tonne is 1000 kg, a US short ton is 2000 lb, and a UK long ton is 2240 lb.
Does this include troy ounces?
No. The ounce option is explicitly avoirdupois; troy mass requires a separate unit.
Sources and review
- NIST Guide to the SI, Appendix B.9: Mass conversion factors — National Institute of Standards and Technology. Accessed 2026-08-30.
- NIST Guide to the SI, Footnotes to conversion-factor tables — National Institute of Standards and Technology. Accessed 2026-08-30.
Reviewed 2026-08-30.