Weight Converter: Kilograms, Pounds, Ounces, Stones
Convert between metric and imperial weight units instantly. Supports milligrams, grams, kilograms, metric tons, ounces, pounds, and stones. Browse all measurement categories at our Unit Converter, or convert lengths with the Length Converter.
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How it works
This converter uses exact mathematical ratios to translate between weight units. All conversions are based on the SI definition of the kilogram and international agreements: one pound equals exactly 0.45359237 kilograms, one ounce is 1/16 of a pound (28.3495 g), and one stone equals 14 pounds (6.35 kg). Metric units scale by powers of ten: 1 metric ton = 1,000 kg = 1,000,000 g.
Enter a value in either field and the converter instantly calculates the result. Use the swap button to reverse the conversion direction. The quick reference table and all-to-all matrix provide common values at a glance.
How Weight Conversion Works
Weight conversion (technically mass conversion) uses fixed ratios to translate values between units. The metric system scales by powers of ten: 1 kilogram equals 1,000 grams, and 1 metric ton equals 1,000 kilograms. The imperial system uses irregular ratios: 1 pound is 16 ounces, and 1 stone is 14 pounds. The key bridge between systems is the international avoirdupois pound, defined as exactly 0.45359237 kilograms. To convert kilograms to pounds, multiply by 2.20462. For grams to ounces, divide by 28.3495.
Common Weight Conversions
The most popular weight conversions are kilograms to pounds (body weight, fitness), grams to ounces (cooking, postal), and pounds to kilograms (travel, luggage). In the UK, stones and pounds are still widely used for body weight — 1 stone equals 14 pounds or 6.35 kilograms. For precious metals, the troy ounce (31.1035 grams) differs from the avoirdupois ounce (28.3495 grams). Metric tons versus short tons matters for shipping: a metric ton is 1,000 kg (2,204.6 lbs), while a US short ton is 2,000 lbs (907.2 kg).
When You Need Weight Conversion
Weight conversion is essential for international cooking (recipe ingredients in grams vs. ounces), fitness and health (body weight, BMI calculations across systems), travel (airline luggage limits typically in kilograms), and shipping (package weight for postal rates). Medical contexts frequently require precise conversions — infant weights reported in pounds and ounces in the US versus kilograms elsewhere. Food labels in Europe list nutritional information per 100 grams, while US labels use serving sizes in ounces. Jewelers and gold traders must distinguish between troy ounces and regular ounces.
Weight Units Around the World
The metric system (grams, kilograms) is the global standard for trade and science. The United States uses pounds and ounces in daily life, though metric units are legal and used in science. The United Kingdom officially uses metric but culturally retains stones for body weight and pounds for many food items. In Germany and Austria, the informal "Pfund" refers to 500 grams (not the 453.6-gram imperial pound). Asian markets sometimes use traditional units like the Chinese jin (500 grams) or Japanese kan (3.75 kg), though metric is the legal standard.
Tips for Accurate Weight Conversion
Use exact conversion factors: 1 kg = 2.20462 lbs, not the rounded 2.2. The error from rounding grows with larger values — at 100 kg, using 2.2 gives 220 lbs instead of the correct 220.46. For cooking, precision below 1 gram rarely matters, but for medication dosages, even milligram accuracy is critical. Always specify which ounce you mean: avoirdupois (28.35 g, everyday) versus troy (31.10 g, precious metals). When shipping internationally, convert and then round up to the next whole unit to avoid surprises at the counter.
Practical Examples
A person weighing 75 kilograms is 165.35 pounds or 11 stone 11.3 pounds. The standard airline carry-on limit of 7 kg equals 15.43 lbs. A 200-gram bar of chocolate weighs 7.05 ounces. A newborn baby at 3.5 kg weighs 7 lbs 11.5 oz. One troy ounce of gold (31.1 g) costs significantly more per gram than a regular ounce. A checked luggage limit of 23 kg is 50.7 pounds.
FAQ
- How do I convert kilograms to pounds?
- Multiply the kilogram value by 2.20462 to get pounds. For example, 70 kg x 2.20462 = 154.32 lbs. For a quick estimate, double the kg value and add 10 percent: 70 x 2 = 140, plus 10% = 154. The exact factor is 1 pound = 0.45359237 kilograms.
- How many grams are in an ounce?
- One avoirdupois ounce equals exactly 28.349523125 grams. To convert ounces to grams, multiply by 28.3495. To convert grams to ounces, divide by 28.3495. For example, 100 grams = 3.527 ounces. Do not confuse the avoirdupois ounce with the troy ounce (31.1035 grams) used for precious metals.
- What is a stone and how do I convert it to kilograms?
- A stone is a British unit of weight equal to 14 pounds or exactly 6.35029318 kilograms. It is primarily used in the UK and Ireland for expressing body weight. To convert stones to kilograms, multiply by 6.35. For example, 12 stone = 76.2 kg = 168 lbs. To convert kg to stones, divide by 6.35 and express the remainder in pounds.
- How do I convert pounds to kilograms?
- Divide the pound value by 2.20462 or multiply by 0.45359237. For example, 150 lbs / 2.20462 = 68.04 kg. For quick mental math, divide pounds by 2.2. The international avoirdupois pound is defined as exactly 0.45359237 kilograms, a definition adopted in 1959.
- What is the difference between a metric ton and a short ton?
- A metric ton (tonne) equals exactly 1,000 kilograms or 2,204.62 pounds. A US short ton equals 2,000 pounds or 907.185 kilograms. A British long ton equals 2,240 pounds or 1,016.047 kilograms. The metric ton is about 10 percent heavier than the short ton and about 1.6 percent lighter than the long ton. Shipping and international trade use metric tons.
- How do I convert body weight between different systems?
- Use these conversions: kilograms to pounds (x 2.20462), pounds to kilograms (/ 2.20462), kilograms to stones and pounds (divide kg by 6.35 for stones, remainder x 14 for pounds). For example, 80 kg = 176.4 lbs = 12 stone 8.4 lbs. BMI calculators accept weight in any unit but convert internally to kg/m2.
- What is a troy ounce and when is it used?
- A troy ounce equals 31.1035 grams, which is about 10 percent heavier than the standard avoirdupois ounce (28.3495 grams). It is the universal standard for weighing precious metals — gold, silver, platinum, and palladium. When gold is quoted at a price per ounce, that always means troy ounces. One troy pound (12 troy ounces = 373.24 g) is lighter than an avoirdupois pound (16 oz = 453.59 g).
- How do I convert cooking weights between grams and ounces?
- Multiply grams by 0.03527 to get ounces, or multiply ounces by 28.3495 to get grams. Common baking conversions: 100 g = 3.5 oz, 200 g = 7.1 oz, 250 g = 8.8 oz, 500 g = 17.6 oz. For precision baking, use a kitchen scale that reads in grams, as most professional recipes worldwide specify weights in metric units.
- What are standard airline luggage weight limits in different units?
- Most international airlines set checked luggage at 23 kg (50.7 lbs) for economy and 32 kg (70.5 lbs) for business/first class. Carry-on limits are typically 7-10 kg (15.4-22 lbs). US domestic flights sometimes list limits in pounds. Always verify your airline's policy and convert to the unit your scale uses before packing to avoid overweight fees.
- How many milligrams are in a gram and when does this matter?
- One gram contains exactly 1,000 milligrams. This conversion is critical in medical and pharmaceutical contexts where medication dosages are specified in milligrams. A typical aspirin tablet is 325 mg (0.325 g), a caffeine tablet is 200 mg (0.2 g), and vitamin C supplements range from 250 to 1,000 mg. Precision to the milligram is essential for patient safety.
- How do I read food nutrition labels in different countries?
- European food labels list nutritional values per 100 grams, making direct comparison between products easy. US labels list values per serving (in grams or ounces) and may have different serving sizes for similar products. To compare: convert the US serving size to 100 grams and scale the nutrient values accordingly. For example, if a US label says 28 g serving with 10 g of fat, per 100 g that is 35.7 g of fat.
- What is the difference between mass and weight?
- Mass measures the amount of matter in an object (kilograms) and does not change with location. Weight is the gravitational force on an object (newtons) and varies with gravity. On Earth, a 1 kg mass has a weight of about 9.81 newtons. On the Moon, the same mass weighs about 1.63 newtons. In everyday use, "weight" and "mass" are used interchangeably because we are always on Earth.
- How do I convert baby weight from pounds and ounces to kilograms?
- First convert everything to ounces (pounds x 16 + ounces), then multiply by 28.3495 to get grams, then divide by 1,000 for kilograms. For example, a baby weighing 7 lbs 8 oz = 120 oz x 28.3495 = 3,401.9 grams = 3.40 kg. Average newborn weight is 3.2-3.5 kg (7 lbs 1 oz to 7 lbs 12 oz).
- What is the German Pfund and how does it differ from the imperial pound?
- In German-speaking countries, a "Pfund" informally refers to 500 grams (exactly half a kilogram), not the imperial pound of 453.59 grams. When a German recipe calls for "ein Pfund Mehl" (a Pfund of flour), it means 500 grams. The imperial pound is called "das englische Pfund" to distinguish it. This regional usage also exists in Austria and parts of Switzerland.
- How do precious metal weights convert between troy and metric?
- Gold and silver are traded in troy ounces: 1 troy ounce = 31.1035 grams. A standard gold bar (London Good Delivery) weighs approximately 400 troy ounces or 12.44 kilograms. One kilogram of gold equals 32.1507 troy ounces. Silver is also priced per troy ounce. When comparing jewelry weight in grams to market prices per troy ounce, divide the gram weight by 31.1035.
- What is a hundredweight and how does it vary by country?
- A hundredweight (cwt) varies by region: the US short hundredweight is 100 pounds (45.36 kg), while the British long hundredweight is 112 pounds (50.80 kg). The metric zentner used in Germany and Austria is exactly 50 kilograms. These units appear in agricultural commodity pricing and historical records. Twenty hundredweights make one ton in their respective systems.