Decision tools built for clarity
Weight and Mass Converter
Convert values between supported mass units.
Enter a mass value, then choose its source unit and target unit.
Methodology
Formula or transformation
Normalizes the submitted mass to kilograms, then applies the target-unit conversion factor.
Variables
- Submitted mass
- Source mass unit factor in kilograms
- Canonical mass in kilograms
- Target mass unit factor in kilograms
- Converted mass
Units
- Milligram
- Gram
- Kilogram
- Metric tonne
- Ounce
- Pound
Rounding policy
The converted mass is rounded to the declared result scale using half away from zero.
The converter maps each supported mass unit through kilograms using fixed SI conversion factors.
Convert values between supported mass units.
Reviewed sources
- NIST — SI conversion factors Reviewed on 2026-09-04
Formula review history
-
Initial formula and source review.
Reviewed 2026-09-04 for formula version nist-mass-conversion-v1
Assumptions
- The input represents mass even where everyday labels use the word weight.
- The selected units use their standard international definitions.
Limitations
- The converter does not calculate force or adjust for local gravity.
- Displayed rounding cannot add precision to the original measurement.
Worked example
Using the international avoirdupois definition, 1 pound = 0.45359237 kilogram exactly.
Frequently asked questions
Does this calculate physical weight force?
No. It converts mass units and does not multiply by gravitational acceleration.
How many kilograms are in a pound?
One international avoirdupois pound is exactly 0.45359237 kilogram.