Weight & Mass Converter
Convert between milligrams, grams, kilograms, tonnes, ounces, pounds, and stone. Shows the conversion factor for verification.
Weight & Mass Converter
Enter a value in any unit β see the conversion in all others instantly. All calculations run in your browser.
Quick References
How to Convert Between Kilograms, Pounds, Stones, and Other Mass Units
A customs declaration form asks for your shipment weight in kilograms, but the scale in your warehouse reads 340 pounds. Submit the wrong number and you risk a customs hold or incorrect duty calculation. Type the weight, choose the unit you have, and every other mass unit updates at once β kilograms, grams, stones, metric tons, US tons, imperial tons. The copy button beside each result lets you paste directly into the declaration form without second-guessing the digits.
The converter handles nine units covering everyday cooking weights through heavy industrial freight. A nutritionist comparing a 6 oz chicken breast to its gram equivalent (roughly 170 g), a gym tracking body weight in stones versus kilograms, or a freight forwarder quoting 4.5 metric tons of cargo in US short tons β all get their answers in one click. The quick-reference row at the bottom translates the current value into everyday objects: a smartphone at 175 g, an average human at 62 kg, an African elephant at 6000 kg.
International shipping where kilograms and pounds collide
An importer in Chicago receives a pallet of electronics from Shenzhen marked 220 kg. The US customs form asks for weight in pounds. Converting 220 kg to pounds gives 485.02 lb. That number determines the per-pound freight rate, which at $0.75/lb changes the shipping cost from $165 to $363.75 β a difference that matters when you are processing dozens of pallets per week. Getting the conversion right the first time avoids reprocessing fees and delayed clearances.
A personal trainer in London logs client weights in kilograms, but their clients report weight in stones. A client who says they weigh "12 stone" is actually 76.2 kg (or 168 lb). The trainer needs to record 76.2 kg in the fitness app, while the client tracks progress on their bathroom scale showing 12 st. This converter bridges the gap instantly β enter 12, select stones, and 76.2007 kg appears alongside 168.000 lb.
A baker in New York follows a British recipe that lists butter as 8 oz. The kitchen scale only reads grams. Converting 8 oz gives exactly 226.796 g β not the 225 g approximation some cookbooks suggest. That 1.8 g difference matters in pastry work where butter-to-flour ratios affect lamination. The tool shows the precise figure so you can decide whether 227 g is close enough or whether to measure exactly.
Related tools
How the Weight Converter Handles Nine Different Mass Scales
The converter stores every unit as a multiple of one kilogram. When you type 150 pounds, it multiplies 150 by 0.45359237 to get 68.0388555 kg, then divides by each target unit's factor to produce grams, stones, metric tons, and so on. Because the kilogram is the hub of every conversion, the result never accumulates rounding from chained multiplications. Converting 1 pound to stones and back to pounds gives exactly 1 lb β the factors are consistent.
Where the imperial mass factors come from
The 1959 International Yard and Pound Agreement defined the pound (avoirdupois) as exactly 0.45359237 kg. From that single definition, all other imperial mass factors follow: 1 ounce = 1/16 lb = 0.028349523125 kg (exact), 1 stone = 14 lb = 6.35029318 kg (exact), 1 US short ton = 2000 lb = 907.18474 kg (exact), and 1 Imperial long ton = 2240 lb = 1016.0469088 kg (exact). These are not rounded numbers β they are exact rational values derived from the pound's definition. The metric factors are even simpler: 1 g = 0.001 kg, 1 mg = 0.000001 kg, 1 metric ton = 1000 kg.
The kilogram itself was redefined in 2019 by fixing the Planck constant at exactly 6.62607015 Γ 10β»Β³β΄ JΒ·s. Before that, the kilogram was defined by a physical platinum-iridium cylinder stored in a vault in SΓ¨vres, France. The redefinition means the kilogram is now anchored to a fundamental constant of nature, making it reprocible anywhere in the universe without reference to a physical artifact.
Why the stone is still used for body weight
The stone (14 lb) persists in the UK, Ireland, and Australia exclusively for human body weight. No grocery store sells produce in stones, no gym weighs equipment in stones β it is a social convention for one specific use case. A person who says "I weigh 10 stone" means 140 lb or 63.5 kg. The stone has no official SI status and was never standardized for commercial trade, which is why it does not appear in scientific or industrial contexts. The converter supports it because millions of people still think in stones when they step on a scale.
The difference between US tons (short tons) and Imperial tons (long tons) matters in heavy industry. A US dump truck rated at 20 short tons carries 18,143.7 kg, while the same truck rated in Imperial long tons would be 18,288.7 kg β about 145 kg more. For mining, shipping, and construction, that 0.8% difference affects load planning and regulatory compliance.
Frequently Asked Questions
How many kilograms is 150 pounds?
150 pounds equals exactly 68.0389 kg. The conversion factor is 1 lb = 0.45359237 kg, defined by international agreement in 1959. For a quick mental estimate, divide the pound value by 2.2 β 150 Γ· 2.2 β 68.2 kg, which is close enough for most purposes. The exact figure matters more in clinical or pharmaceutical contexts where dosage depends on precise body mass.
What is the difference between a US ton and an Imperial ton?
A US ton (short ton) is exactly 2,000 pounds or 907.185 kg. An Imperial ton (long ton) is exactly 2,240 pounds or 1,016.047 kg β about 12% heavier. In US mining and trucking, a payload rated at 25 short tons is 22,679.6 kg. The same rating in the UK would be 25 long tons, or 25,401.2 kg. Always check which ton is being used when quoting freight across the Atlantic.
Why do British people weigh themselves in stones?
The stone (14 lb) has been used for body weight in Britain since the Middle Ages. It survived metrication because it produces convenient numbers: a person who weighs 70 kg can say 11 stone rather than 154 lb. The stone is not used for anything else in the UK β nobody buys 2 stones of apples. It exists purely as a social convention for personal weight, and most bathroom scales in the UK have a stone toggle switch.
How do I convert grams to ounces for a recipe?
Divide the gram value by 28.3495. A 200 g block of butter is approximately 7.055 oz. Most American cookbooks round this to 7 oz, which is a 0.8% error β acceptable for cookies but potentially problematic for precision baking like macarons where ratios are critical. This tool shows the exact result so you can decide whether the rounded version is close enough for your recipe.
Is 1 kg the same as 2.2 pounds?
Almost. 1 kg equals exactly 2.20462 lb, so 2.2 lb is a 0.21% underestimate. For everyday purposes β estimating luggage weight, comparing grocery prices, tracking fitness progress β 2.2 is close enough. For pharmaceutical dosing, engineering load calculations, or customs declarations, use the exact 2.20462 factor. This tool provides the precise result to 6+ significant digits.