What is a weight converter?
Convert weight and mass among metric, U.S. customary and imperial units, including kilograms, pounds, ounces, stone, tons, and tonnes. It is designed for quick everyday and technical unit comparisons without requiring sign-up or server-side calculation.
How does this converter work?
The calculator converts the entered value through a common reference unit or an exact scale relationship, then converts that reference value to the selected target unit. Intermediate values are not rounded. This follows the general NIST approach of choosing an appropriate conversion factor, canceling units and rounding the final quantity rather than intermediate steps.
Which units are supported?
Milligrams, grams, kilograms, metric tonnes, ounces, pounds, stone, U.S. short tons and imperial long tons.
Use the unit labels carefully when similar names can represent different systems. The selected units are always shown again in the result panel.
How do you use this weight converter?
- Enter the numerical value you want to convert.
- Select the starting unit.
- Select the target unit, or use Swap Units to reverse them.
- Keep precision on Automatic or choose a significant-digit setting.
- Select Convert, then review the conversion relationship and result details.
Conversion example
1 pound equals exactly 0.45359237 kilograms under the international avoirdupois definition.
Accuracy, definitions and rounding
This everyday “weight” converter converts mass units. It does not convert force units such as newtons or pound-force.
For important engineering, scientific, commercial or regulatory work, confirm that the unit definition, measurement uncertainty and required significant digits match the standards used in your application.
Mass, everyday weight labels and measured quantities
Everyday product labels often use the word weight for quantities expressed in kilograms, grams, pounds and ounces. In physics, those units describe mass, while weight is a force that depends on gravity. For shopping, shipping and recipe work, the everyday mass convention is normally what the printed unit intends, but technical documents should be read according to their definitions.
A mass conversion cannot convert a cup, litre or other volume directly into grams without knowing the material's density. That is why ingredient and liquid conversions may need a product-specific value rather than a universal factor. For parcels, use the carrier's required unit and do not confuse actual mass with dimensional shipping weight. When a scale reading is the source, match the result's decimal places to the scale's resolution instead of adding digits that were never measured.
Frequently asked questions
Sources and methodology
The calculation relationships and explanatory notes are based on authoritative measurement references. Links open the original source so you can verify the unit definitions and conversion guidance.