Mass and everyday weight

Mass measures the amount of matter, while weight is a force that depends on gravity. Everyday scales and product labels commonly use “weight” while reporting mass units such as kilograms or pounds. This converter follows that everyday convention and converts the mass represented by each unit.

International pound, ounce, and stone

The international avoirdupois pound is defined as exactly 0.45359237 kilogram. One avoirdupois ounce is exactly one-sixteenth of a pound, and one stone equals 14 pounds. These definitions make the conversion factors exact even though a measured object may not have exact mass.

Worked examples

Ten pounds equals 4.5359237 kilograms. Eleven stone equals 154 pounds before conversion, or about 69.8532 kilograms. For a smaller metric example, 250 grams equals 0.25 kilogram and approximately 8.8185 avoirdupois ounces.

Metric prefixes

One kilogram equals 1,000 grams, and one gram equals 1,000 milligrams. Moving from grams to milligrams multiplies by 1,000; moving from grams to kilograms divides by 1,000. Writing the unit beside every intermediate value helps prevent a factor-of-1,000 error.

Precision and unit names

A scale reading to the nearest gram does not justify a converted answer accurate to a fraction of a milligram. Keep extra digits during related calculations, then round the final answer to the precision supported by the scale. Also distinguish mass ounces from fluid ounces, which measure volume.

This tool uses international avoirdupois units, not troy ounces used for precious metals or fluid ounces used for volume. Verify standards, labeling rules, and scale calibration for medical, trade, shipping, or regulated work.