Weight / Mass Converter

Metric and imperial mass units

This converter covers tonnes, kilograms, grams, milligrams and micrograms for metric work, plus pounds, ounces, stones and US short tons for imperial measurements. It also includes the carat, used for gemstones and pearls.

Conversions use the international avoirdupois pound (1 lb = 453.59237 g) so results match scientific and commercial standards exactly.

Popular weight conversions

• Kilograms to pounds and pounds to kilograms
• Grams to ounces and ounces to grams
• Stones to kilograms for body weight
• Tonnes and US tons for bulk material

Key features at a glance

• Metric units: tonnes, kilograms, grams, milligrams, micrograms
• Imperial units: pounds, ounces, stones, and US short tons
• Includes the carat for gemstones and pearls
• Live conversion table updates as you type
• Based on the international avoirdupois pound for exact results
• Runs entirely in your browser, even offline

Mass versus weight

In everyday speech we use 'weight' and 'mass' interchangeably, but in physics they are different things. Mass is the amount of matter in an object and never changes, whereas weight is the force gravity exerts on that mass and varies with location — you would weigh less on the Moon though your mass is identical. The units this tool converts, like kilograms and pounds, are technically mass units.

For practical purposes on Earth, where gravity is effectively constant, the distinction rarely matters, which is why a bathroom scale can report 'weight' in kilograms. This converter treats them as everyday mass measurements, so whether you are weighing groceries, body weight, or freight, the conversions behave exactly as you expect for any task that stays on the ground.

The avoirdupois system and the pound

The pound used in commerce and daily life is the international avoirdupois pound, defined as exactly 453.59237 grams. Avoirdupois — from an old French phrase meaning 'goods of weight' — is the system that gives us the familiar 16 ounces to a pound. Anchoring the pound to a precise number of grams ties the imperial system directly to the metric one, so conversions are exact rather than approximate.

The stone, equal to 14 pounds, remains common in Britain and Ireland for body weight, while the US short ton is 2,000 pounds. Knowing these relationships explains some quirks: a US ton and a metric tonne are close but not identical, and the troy ounce used for precious metals is different again from the avoirdupois ounce, a distinction worth remembering when weighing gold or silver.

Carats, grams, and specialized units

Some fields use their own mass units. The carat, used for diamonds and other gemstones, is defined as exactly 200 milligrams, so a five-carat stone weighs one gram. This precise definition lets jewelers and buyers communicate weights unambiguously, and the converter includes it for exactly that purpose.

At the other end of the scale, micrograms and milligrams matter in medicine and chemistry, where dosages and quantities are tiny but precision is critical. Having every unit from the microgram to the tonne in one place means you can move between a pharmaceutical dose and a bulk shipment weight without switching tools, with each conversion grounded in exact, standardized definitions.

Tips for converting weight

• Remember 1 kg is about 2.205 lb for quick mental estimates
• Use stones for body weight when reading British measurements
• A carat is exactly 200 mg — five carats make one gram
• Watch for troy versus avoirdupois ounces when weighing precious metals
• Distinguish the metric tonne from the slightly smaller US short ton

Why choose our weight / mass converter?

Our converter is completely free with no signup, no limits, and no subscription. It runs entirely in your browser, so conversions are instant, it works offline, and the values you enter never leave your device.

It is one of more than 200 free tools on ToopTools, and you can pin it to your My Workspace, a personalized workspace where you keep the tools you use most in a single dashboard. Beside the other unit converters, it covers every mass conversion from gemstones to freight in one place.

Common use cases

People use the weight converter for cooking with recipes that mix grams and ounces, for tracking body weight across kilograms, pounds, and stones, and for shipping where parcel weights must meet limits in different units. It turns confusing cross-system weights into clear, exact figures.

Jewelers and gem buyers use the carat, scientists and pharmacists use milligrams and micrograms, and anyone dealing with bulk materials uses tonnes and tons. Because the converter shows every unit at once, you instantly see a weight expressed in whichever measure your task requires.

Is the weight converter free?

Yes. It is completely free with no account, no sign-up, and no usage limits. Convert as many weights as you like at no cost.

How many pounds are in a kilogram?

One kilogram is approximately 2.20462 pounds. The relationship comes from the avoirdupois pound being defined as exactly 453.59237 grams, so the converter gives an exact result rather than a rounded one.

What is the difference between mass and weight?

Mass is the amount of matter in an object and is constant, while weight is the force of gravity on that mass and varies with location. On Earth the distinction rarely matters, so everyday 'weight' figures convert just as you expect.

How heavy is a carat?

A carat is exactly 200 milligrams, or one-fifth of a gram. It is used for gemstones and pearls, so a five-carat diamond weighs exactly one gram.

Is a US ton the same as a metric tonne?

No. A US short ton is 2,000 pounds (about 907 kg), while a metric tonne is 1,000 kg (about 2,205 lb). They are close but not equal, so the converter keeps them separate.

Are my conversions kept private?

Yes. Everything is computed in your browser and nothing is uploaded, so the values you enter stay private and the tool works without an internet connection.

How do I convert kilograms to pounds and ounces?

Enter a weight in kilograms, choose pounds or ounces as the target unit, and the converter shows the result instantly. It also handles grams, milligrams, stones, carats, and tons, so you can move between metric and imperial weights in a single step.

Does the weight converter work offline?

Yes. The conversion runs entirely in your browser, so once the page has loaded the tool works without an internet connection, and nothing you enter is uploaded — it stays private on your own device.