Weight & Mass Converter

Convert between kilograms, pounds, ounces, grams, stones, metric tonnes, and US/long tons — for shipping, cooking, body weight, and science.

Weight & Mass

kg, lb, oz, tonnes

From

Result

1000

1 kg = 1000 g

Popular conversions

What Is a Weight & Mass Converter?

A weight converter translates a measurement of mass — kilograms to pounds, grams to ounces, tonnes to tons — from one unit to another. Strictly, mass (how much matter) and weight (the force gravity exerts on it) are different, but in everyday use on Earth's surface they track together, and 'weight' converters work in mass units. The kilogram is the SI base unit, and since 2019 it has been defined by a fixed value of the Planck constant rather than a metal cylinder in Paris.

This converter handles the everyday split between metric (kilogram, gram, tonne) and imperial/US (pound, ounce, stone, ton). One pound is exactly 0.45359237 kg, and there are 16 ounces to a pound and 14 pounds to a stone. It also distinguishes the metric tonne (1,000 kg) from the US short ton (907 kg) and the UK long ton (1,016 kg).

This is one category of the full Unit Converter — pair it with our percentage calculator or scientific calculator for related everyday maths.

How Weight Conversion Works

Everything routes through the kilogram

Each unit has a fixed kilogram factor. The converter turns your input into kilograms, then projects it into every other mass unit so all outputs agree.

The pound is exactly defined

Since 1959, one pound is exactly 0.45359237 kg, making all metric–imperial mass conversions exact rather than approximate.

Imperial mass uses mixed steps

16 ounces to a pound, 14 pounds to a stone, 2,240 lb to a long ton. These non-decimal steps are exactly where a converter earns its keep.

Three different 'tons'

The metric tonne is 1,000 kg, the US short ton 907.18 kg, and the UK long ton 1,016.05 kg — always check which one a figure means.

Core Weight Conversion Factors

Multiply to reach kilograms; divide to come back. The pound factor is exact.

Pounds → kg

× 0.453592

One pound is exactly 0.45359237 kg. The anchor of all metric–imperial weight conversions.

Ounces → grams

× 28.349523

One ounce is 28.349523 grams. Sixteen ounces make a pound.

Stones → kg

× 6.350293

One stone is 14 pounds, or 6.350293 kg. Used for body weight in the UK and Ireland.

How to Use the Weight Converter

1
Enter the weight
Type the mass you want to convert — body weight, an ingredient, a parcel, a cargo load.
2
Choose the 'from' unit
Pick kilograms, pounds, ounces, grams, stones, tonnes, or tons. Mind which 'ton' you mean.
3
Choose the 'to' unit
Select the target unit, or swap the two to reverse the conversion.
4
See every unit at once
The all-units table converts your value into kilograms, pounds, ounces, grams, stones, and tonnes together.

Key Weight & Mass Concepts

Mass vs weight

Mass is the amount of matter (kilograms); weight is the gravitational force on it (newtons). On Earth they're proportional, so everyday 'weight' converters use mass units.

Kilogram

The SI base unit of mass, redefined in 2019 in terms of the Planck constant. Every other mass unit is a fixed multiple of it.

Stone

An imperial unit of 14 pounds (6.35 kg), still used for body weight in the UK and Ireland. A 70 kg person weighs about 11 stone.

Tonne vs ton

The metric tonne is 1,000 kg; the US short ton is 2,000 lb (907 kg); the UK long ton is 2,240 lb (1,016 kg). Three units, one easily confused word.

Real-World Weight Conversions

⚖️

Body weight

A 70 kg adult is 154 lb or about 11 stone. Health and fitness apps switch between kg, pounds, and stones by region.

🥘

Recipe ingredients

200 g of flour is about 7 oz; 1 lb of butter is 454 g. Baking by weight is more accurate than by volume, so the conversion matters.

📦

Parcel shipping

A 5 kg parcel is 11 lb; carriers price by weight bands, so converting correctly can change the shipping tier and cost.

🏋️

Gym plates

A 20 kg Olympic plate is 44 lb; a 45 lb US plate is 20.4 kg. Lifters convert between metric and imperial loading constantly.

🚚

Cargo and freight

A 10-tonne load is 11.02 US short tons or 9.84 long tons. Choosing the wrong 'ton' misstates a load by up to 10%.

💎

Precious materials

Gold is weighed in troy ounces (31.1 g), heavier than the standard ounce (28.35 g) — a distinction worth real money.

Best Practices for Weight Conversion

✓Keep the pound exact at 0.45359237 kg. The pound is precisely defined, so metric–imperial weight conversions are exact. Avoid the rough '2.2 lb per kg' for anything that needs precision.
✓Specify which ton you mean. Metric tonne, US short ton, and UK long ton differ by up to 10%. Always label the unit in shipping and cargo figures.
✓Use grams for small precise weights. For baking, lab work, and dosing, grams beat ounces — they avoid the 16ths and fractions that introduce rounding error.
✓Watch troy vs avoirdupois ounces. Precious metals use the troy ounce (31.1 g); everything else uses the standard ounce (28.35 g). Mixing them misvalues metals.
✓Don't confuse mass with weight in physics. For force and acceleration problems, keep mass in kilograms and compute weight as mass × gravity — the everyday shortcut breaks off-Earth.

Common Weight Conversion Mistakes

Using 2.2 lb/kg for precise work

The real factor is 2.20462 lb/kg. The rounded 2.2 is 0.2% low — fine for a gym estimate, wrong for a calibrated scale or shipping tier.

Confusing the three tons

Metric tonne, short ton, and long ton differ by up to ~10%. Using the wrong one misstates a cargo load and its cost.

Mixing troy and standard ounces

A troy ounce is ~10% heavier than a regular ounce. Confusing them in precious-metal trades is an expensive error.

Treating kg as a weight off Earth

Mass stays constant everywhere; weight changes with gravity. The everyday kg↔lb shortcut assumes Earth's surface gravity.

Why Weight Conversion Matters

Weight is how goods are priced and shipped, how recipes and medicines are dosed, and how health and fitness are tracked. The metric–imperial divide runs straight through all of it: a parcel weight, a body weight, an ingredient, or a cargo load can be quoted in kilograms, pounds, stones, or one of three different tons depending on who you're dealing with.

Getting it wrong costs money or worse — a shipping tier crossed, a recipe thrown out of proportion, a cargo load misjudged, or a dose miscalculated. A converter that uses the exact pound definition and keeps the tonne/short-ton/long-ton and troy/standard-ounce distinctions straight removes the arithmetic risk from a measurement that often has real financial or safety stakes.

Built for shippers, cooks, lifters, healthcare workers, travellers, and anyone moving between kilograms, pounds, stones, and tonnes.

Linear unit factors follow the BIPM SI brochure, the NIST Guide to the SI, and ISO 80000. Currency rates load live from open.er-api.com; crypto prices from CoinGecko. See our methodology and editorial policy. Educational only — not certified for regulated trading, settlement, medical, or aerospace use.

Weight Converter FAQs

Multiply kilograms by 2.20462 to get pounds. So 70 kg = 154.3 lb. To go the other way, multiply pounds by 0.453592 to get kilograms. The pound is defined as exactly 0.45359237 kg, so the conversion is exact; the rounded '2.2' factor is slightly low for precise work.

One standard (avoirdupois) ounce is 28.3495 grams, and 16 ounces make a pound. Note that precious metals use the troy ounce, which is heavier at 31.1035 grams — so the kind of ounce matters when weighing gold or silver.

Mass is the amount of matter in an object, measured in kilograms and constant everywhere. Weight is the gravitational force on that mass, measured in newtons and dependent on local gravity. On Earth's surface they're proportional, which is why everyday 'weight' converters work in mass units.

One stone equals 14 pounds, or about 6.35 kilograms. The stone is still commonly used for body weight in the UK and Ireland — a 70 kg person weighs about 11 stone (11 st 0.5 lb).

A metric tonne is 1,000 kg (2,205 lb). A US short ton is 2,000 lb (907 kg), and a UK long ton is 2,240 lb (1,016 kg). The three differ by up to about 10%, so cargo and freight figures should always state which ton is meant.

It uses exact definitions (pound = 0.45359237 kg, ounce = 1/16 lb, stone = 14 lb, tonne = 1,000 kg) and routes every conversion through kilograms at full precision, so the result is exact to your input precision.