Mass Converter

Convert between kilograms, grams, pounds, ounces, and other mass units. Check which ounce you need: precious metals use troy ounces, while everyday weights usually use avoirdupois ounces. They have different sizes. Choose the matching unit before entering your value, then use the formula and examples to check the conversion.

Mass Conversion Guide

Understanding Mass Measurements

The kilogram is the SI base unit of mass, redefined in 2019 by fixing the Planck constant at exactly 6.626 070 15 × 10⁻³⁴ J·s. The gram (1/1000 kg), milligram, and tonne (1000 kg) follow SI prefix convention. The avoirdupois pound (used for everyday commerce in the US) is defined as exactly 453.592 37 g. The troy pound (for precious metals) is 373.241 72 g, making a troy ounce (31.103 g) heavier than an avoirdupois ounce (28.350 g) by about 10%.

All conversions in this category are computed relative to a single base unit (Kilogram) using factors sourced from NIST Special Publication 811 and the BIPM SI Brochure. A shared reference unit keeps the conversion relationships consistent. Converting directly from the original measurement avoids the rounding differences that can accumulate when displayed intermediate results are entered again.

Common Mass Units

This calculator supports 10 units, including Kilogram, Gram, Milligram, Microgram, Metric Ton. Choose the unit shown in your source measurement, then the unit needed for your result.

Units may have alternate spellings or abbreviations. You can search using these names too. Examples include Kilogram (kg, also written as kilograms or kilo), or Gram (g, also written as grams or gramme), or Milligram (mg, also written as milligrams or milligramme).

How to Convert Mass Accurately

All mass conversions within the SI family are purely multiplicative: you multiply the source value by a fixed conversion factor derived from the ratio of the two unit definitions. Imperial-to-metric conversions use the exact defined equivalences (e.g., 1 inch = 25.4 mm exactly) rather than approximations.

When precision matters, avoid rounding intermediate calculations. The displayed factors and results are rounded for readability, usually to ten significant digits; very large or small values use scientific notation. Use the original measurement for each conversion and round the final answer to match the accuracy of that measurement.

Checking Your Mass Conversion

Keep the unit alongside each mass value when you copy or share it. Check that the source and target units match your task. If two units have similar names, read their definitions before selecting one.

For a second check, use the worked example and formula on the conversion page. Start from your original value rather than a rounded result from another calculator. If you need to report a specific number of decimal places, round once at the end.

Available Mass Units

See full definitions in the unit glossary →

Kilogram(kg)

Also: kilograms, kilo

Gram(g)

Also: grams, gramme

Milligram(mg)

Also: milligrams, milligramme

Microgram(ug)

Also: micrograms, mcg

Metric Ton(t)

Also: tonne, tonnes

Pound(lb)

Also: pounds, lbs

Ounce(oz)

Also: ounces

Stone(st)

Also: stones

US Ton(ton)

Also: short ton, us tons

Imperial Ton(long-ton)

Also: long ton, uk ton

Popular Mass Converters

Choose a pair below, or browse the full list for other units.

Kilogram to Gramkg to g Kilogram to Milligramkg to mg Kilogram to Metric Tonkg to t Kilogram to Poundkg to lb Kilogram to Ouncekg to oz Kilogram to Stonekg to st Kilogram to US Tonkg to ton Kilogram to Imperial Tonkg to long-ton Gram to Kilogramg to kg Gram to Milligramg to mg

All Mass Converters

Each page has a calculator, a formula, and examples you can check by hand.

Kilogram to Gramkg ⇄ g Kilogram to Milligramkg ⇄ mg Kilogram to Metric Tonkg ⇄ t Kilogram to Poundkg ⇄ lb Kilogram to Ouncekg ⇄ oz Kilogram to Stonekg ⇄ st Kilogram to US Tonkg ⇄ ton Kilogram to Imperial Tonkg ⇄ long-ton Gram to Kilogramg ⇄ kg Gram to Milligramg ⇄ mg Gram to Microgramg ⇄ ug Gram to Poundg ⇄ lb Gram to Ounceg ⇄ oz Gram to Stoneg ⇄ st Gram to Imperial Tong ⇄ long-ton Milligram to Kilogrammg ⇄ kg Milligram to Grammg ⇄ g Milligram to Microgrammg ⇄ ug Milligram to Poundmg ⇄ lb Milligram to Ouncemg ⇄ oz Milligram to Stonemg ⇄ st Milligram to Imperial Tonmg ⇄ long-ton Microgram to Gramug ⇄ g Microgram to Milligramug ⇄ mg Microgram to Poundug ⇄ lb Microgram to Ounceug ⇄ oz Microgram to Stoneug ⇄ st Microgram to Imperial Tonug ⇄ long-ton Metric Ton to Kilogramt ⇄ kg Metric Ton to Poundt ⇄ lb Metric Ton to Ouncet ⇄ oz Metric Ton to Stonet ⇄ st Metric Ton to Imperial Tont ⇄ long-ton Pound to Kilogramlb ⇄ kg Pound to Gramlb ⇄ g Pound to Milligramlb ⇄ mg Pound to Microgramlb ⇄ ug Pound to Metric Tonlb ⇄ t Pound to Ouncelb ⇄ oz Pound to Stonelb ⇄ st Pound to US Tonlb ⇄ ton Ounce to Kilogramoz ⇄ kg Ounce to Gramoz ⇄ g Ounce to Milligramoz ⇄ mg Ounce to Microgramoz ⇄ ug Ounce to Metric Tonoz ⇄ t Ounce to Poundoz ⇄ lb Ounce to US Tonoz ⇄ ton Stone to Kilogramst ⇄ kg Stone to Gramst ⇄ g Stone to Milligramst ⇄ mg Stone to Microgramst ⇄ ug Stone to Metric Tonst ⇄ t Stone to Poundst ⇄ lb Stone to US Tonst ⇄ ton US Ton to Kilogramton ⇄ kg US Ton to Poundton ⇄ lb US Ton to Ounceton ⇄ oz US Ton to Stoneton ⇄ st US Ton to Imperial Tonton ⇄ long-ton Imperial Ton to Kilogramlong-ton ⇄ kg Imperial Ton to Gramlong-ton ⇄ g Imperial Ton to Milligramlong-ton ⇄ mg Imperial Ton to Microgramlong-ton ⇄ ug Imperial Ton to Metric Tonlong-ton ⇄ t Imperial Ton to US Tonlong-ton ⇄ ton

Mass Converter FAQ

How many mass units are supported?

This category supports 10 units: Kilogram, Gram, Milligram, Microgram, Metric Ton, Pound, Ounce, Stone, US Ton, Imperial Ton.

How do I convert mass units?

Choose a source and target unit, enter a value, and multiply through the kg base-unit factors shown on the dedicated converter page.

Which mass conversion should I start with?

Choose the pair that matches your measurement. For example, the Kilogram to Gram page shows its formula and worked examples. Related links let you reverse the conversion or choose another unit.

Can I look up mass values in a reference table?

Yes. Open a conversion pair to see worked examples and a table of common input values. These reference values remain readable without running the interactive calculator. For an input not listed, use the displayed formula or enter it in the calculator.

How should I round a mass conversion?

Match the precision of your original measurement. Keep extra digits during the calculation, then round the final answer to the required decimal places or significant figures. Displaying more digits does not make the original measurement more accurate.