PRACTICAL GUIDE / REVIEWED
Understanding mass units
Mass measures the amount of matter in an object. The kilogram is the SI base unit, and metric units scale by powers of ten. The international avoirdupois pound is exactly 0.45359237 kilograms; ounces and stones in this guide derive from that same system.
Where these units are used
Grams and kilograms are used for food, science, medicine, shipping, and body mass. Milligrams suit small quantities. Pounds and ounces are common in the United States, stone is still used informally for body mass in the United Kingdom, and tonnes describe large freight or industrial loads.
Rounding and precision
Match the result to the scale and quality of the measurement. A kitchen scale may justify whole grams, while freight may be rounded to kilograms. Keep guard digits for multi-step work and avoid presenting a converted value as more accurate than the source.
Regional differences
This category uses the international avoirdupois pound and ounce. It does not represent troy ounces used for precious metals. A metric tonne is 1,000 kilograms and is not the same as a US short ton or Imperial long ton.
Common mistakes
Mass and force are different quantities. A kilogram is not a newton or kilogram-force. Also check whether an unlabeled 'ounce' means avoirdupois mass, fluid volume, or troy mass before converting.
USEFUL ANSWERS
Mass conversion FAQs
How many ounces are in an avoirdupois pound?
There are exactly 16 avoirdupois ounces in one international avoirdupois pound.
Is a tonne the same as a ton?
Not necessarily. A metric tonne is 1,000 kg; US short tons and Imperial long tons are different.
Why is weight listed under mass?
Everyday speech often says weight for mass. The converter's kg, g, lb, oz, and stone entries are mass units; force units are in the Force category.