Mass converter

How to use the mass converter

1. Enter the numeric mass in the left field. Use a decimal point rather than a comma, and leave the unit symbol out of the field.
2. Choose the current unit under From unit and the unit you need under To unit. The six choices are g, kg, metric tonne, lb, commercial oz, and stone.
3. Select Convert mass or press Enter. Editing the number clears the previous answer; after a successful conversion, changing either unit recalculates immediately.
4. Read the main answer and both mixed-unit lines. Use Copy result to copy a labeled statement, or Swap units to exchange the two unit selections.

Conversion method and unit definitions

The converter relates every unit to kilograms, then divides by the kilogram value of the destination unit. Metric relationships are direct: 1 kilogram is 1,000 grams and 1 metric tonne is 1,000 kilograms. The word tonne on this page always means the metric tonne, not the 2,000-pound US short ton or the 2,240-pound UK long ton.

For customary units, the international avoirdupois pound is exactly 0.45359237 kilogram. One avoirdupois pound contains 16 avoirdupois ounces, so one ounce is exactly 28.349523125 grams. One stone contains 14 pounds and therefore equals 6.35029318 kilograms. Calculations keep these full factors internally and round only the displayed result.

The ounce choice is the ordinary commercial, food, postal, and household ounce. It is not the troy ounce used for precious metals. A troy ounce is about 31.1035 grams, so substituting it would produce a different answer. The unit label explicitly says avoirdupois to make this boundary visible before conversion.

The main result normally shows no more than two decimal places and removes unnecessary trailing zeros. Small positive values retain enough significant digits to avoid appearing as zero, while very small or large values use compact scientific notation. The mixed lines split the full internal mass at whole-pound or whole-stone boundaries; if rounding reaches 16 oz or 14 lb, the value carries into the next larger unit.

Worked mass conversion examples

Where these conversions are useful

• Compare package, luggage, freight, workshop, or product specifications written in different metric and customary units.
• Translate a recipe ingredient measured by mass between grams and ordinary ounces. The tool does not convert cups, tablespoons, or fluid ounces.
• Record a scale reading in kilograms, pounds, or the stone-and-pound notation commonly used for body mass in the UK and Ireland. It does not interpret health ranges.
• Check classroom calculations and labeled estimates while keeping the original measurement and unit beside the converted result.

Input, precision, and practical limits

• Zero is valid. Negative values, blank input, unit text, grouping separators, and malformed numbers are rejected without deleting what you typed.
• Use a point as the decimal separator in all six language versions. For example, enter 1.5 rather than 1,5. Scientific notation such as 2.5e-4 is accepted.
• Displayed rounding does not increase the accuracy of the original measurement. Keep appropriate significant figures for laboratory, engineering, trade, or regulated work.
• The converter handles mass only. It does not turn mass into volume because that requires material density, and it does not convert mass into force or newtons because that requires acceleration.
• Tonne means exactly 1,000 kg. US short tons, UK long tons, troy ounces, grains, carats, and other specialist units are outside this page.
• Copy result creates clipboard text but no saved history or cloud record. Paste the result into your own notes before closing the tab if you need to keep it.

Frequently asked questions