Weight Converter

Convert Weight Units Online — Kilograms, Pounds, Ounces, and More

Our free weight converter lets you instantly switch between metric and imperial weight units with precision. Whether you need to convert kg to lbs for a fitness goal, grams to ounces for a recipe, or tons to kilograms for a shipping manifest, this tool delivers accurate results in real time. All calculations run directly in your browser — no data is sent to any server, and no sign-up is required.

How to Convert Between Weight Units

Weight unit conversion uses fixed multiplication factors between units. Once you know the correct factor, the math is straightforward. Below are the most commonly needed formulas with worked examples for each conversion.

Kilograms to Pounds

The formula is pounds = kilograms × 2.20462. One kilogram equals approximately 2.20462 pounds. For example, to convert 70 kg: 70 × 2.20462 = 154.32 lbs. This is one of the most frequently searched weight conversions worldwide, used in fitness tracking, medical records, and international shipping. A quick approximation is to double the kilogram value and add 10 percent — 70 kg becomes 140 + 14 = 154 lbs, which is remarkably close to the exact answer.

Pounds to Kilograms

The formula is kilograms = pounds × 0.453592. One pound equals approximately 0.453592 kilograms. For example, to convert 150 lbs: 150 × 0.453592 = 68.04 kg. This conversion is essential when traveling between countries that use different systems, filling out medical forms abroad, or comparing product weights listed in different units.

Grams to Ounces

The formula is ounces = grams × 0.035274. One gram equals approximately 0.035274 ounces. For example, to convert 250 grams: 250 × 0.035274 = 8.82 ounces. Cooking and baking are the primary scenarios for this conversion, as European recipes use grams while many American recipes use ounces. A standard stick of butter weighs 113 grams or 4 ounces.

Ounces to Grams

The formula is grams = ounces × 28.3495. One ounce equals approximately 28.3495 grams. For example, to convert 8 ounces: 8 × 28.3495 = 226.8 grams. This is the inverse of the grams-to-ounces conversion and appears frequently in food packaging, postal services, and precious metal trading.

Stones to Kilograms and Pounds

The formula is kilograms = stones × 6.35029 and pounds = stones × 14. One stone equals exactly 14 pounds or approximately 6.35029 kilograms. The stone is commonly used in the United Kingdom and Ireland for expressing body weight. For example, a person weighing 12 stone is 168 pounds or 76.2 kilograms. While less common internationally, this unit still appears on British scales and in casual conversation across the UK.

Metric Tons to Pounds

The formula is pounds = metric tons × 2204.62. One metric ton (also called a tonne) equals 1,000 kilograms or approximately 2,204.62 pounds. For example, a shipping container rated at 20 metric tons can hold up to 44,092 pounds. Note that a US short ton equals 2,000 pounds (907.185 kg) and a British long ton equals 2,240 pounds (1,016.05 kg). Always verify which type of ton is being referenced in shipping and industrial contexts to avoid costly errors.

About the Weight Converter

Weight and mass measurement is central to cooking, fitness, medicine, commerce, manufacturing, and scientific research. Different countries and industries rely on different unit systems, making a dependable mass converter essential for anyone working across borders or disciplines. This converter supports milligrams, grams, kilograms, metric tons, ounces, pounds, stones, and both short and long tons, covering virtually every common weight measurement need.

Understanding Mass, Weight, and Their Units

In everyday language, "weight" and "mass" are used interchangeably, but in physics they are distinct concepts. Mass is the amount of matter in an object, measured in kilograms in the SI system. Weight is the force exerted on that mass by gravity, technically measured in newtons. On Earth's surface, the distinction rarely matters for practical purposes because gravity is essentially constant. However, an astronaut with a mass of 70 kg would weigh about 70 kg-force on Earth but only about 11.7 kg-force on the Moon, while their mass remains 70 kg in both locations. For everyday conversions — cooking, shipping, fitness — treating mass and weight as equivalent is perfectly acceptable.

The metric system of mass measurement centers on the kilogram, which was originally defined in 1795 as the mass of one liter of water at 4 degrees Celsius. In 1889, a physical platinum-iridium cylinder stored in Paris became the International Prototype of the Kilogram. This artifact served as the world standard for over a century until 2019, when the kilogram was redefined in terms of the Planck constant, a fundamental physical constant. This new definition ensures the kilogram can be precisely reproduced in any well-equipped laboratory without reference to a physical object.

Imperial and US customary weight units have roots in medieval trade. The pound derives from the Roman "libra pondo" (hence the abbreviation "lb"), and the ounce comes from the Latin "uncia," meaning one-twelfth. The avoirdupois system, used for most everyday weighing in English-speaking countries, defines one pound as exactly 0.45359237 kilograms. The troy system, still used for precious metals, defines a troy ounce as 31.1035 grams — heavier than the avoirdupois ounce of 28.3495 grams. When gold or silver prices are quoted per ounce, they always mean troy ounces.

Common Weight Conversions in Daily Life

Cooking and baking are among the most frequent reasons people convert weight units. Professional bakers worldwide measure ingredients by weight rather than volume because it is far more accurate. A European recipe calling for 200 grams of flour needs to be converted to roughly 7.05 ounces for an American kitchen scale set to imperial units. Butter, sugar, and chocolate are commonly sold in different package sizes across countries — a 250-gram block of butter is about 8.82 ounces or just over half a pound. Our kg to lbs converter is especially popular for scaling recipes between metric and imperial measurements.

Fitness and health tracking rely heavily on weight conversions. Gym equipment in the United States is typically labeled in pounds, while most of the world uses kilograms. A person who bench presses 100 kg is lifting 220.46 pounds. Bodyweight is another constant conversion need: medical records in most countries use kilograms, but Americans think in pounds. A 180-pound person weighs 81.65 kilograms. Nutritional labels also vary — protein, fat, and carbohydrate content may be listed per 100 grams in one country and per serving in ounces in another.

Shipping and logistics depend on accurate weight conversions every day. International freight is typically quoted in metric tons, while domestic US trucking uses short tons and pounds. A container rated for 24 metric tons can carry 52,911 pounds. Postal services have weight limits in different units — the US Postal Service uses pounds and ounces, while most international carriers use grams and kilograms. Overweight packages incur surcharges, so precise conversion matters financially. Air freight is particularly weight-sensitive, with rates calculated per kilogram in most markets.

Precious metals and gemstones use specialized weight units. Gold and silver are traded in troy ounces (31.1035 grams), not the standard avoirdupois ounces (28.3495 grams). Diamonds and other gemstones use carats, where one carat equals 0.2 grams or 200 milligrams. A 1-carat diamond weighs just 0.00705 avoirdupois ounces. Confusing troy and avoirdupois ounces when buying or selling precious metals can lead to significant financial errors.

Tips and Quick Reference

A fast mental shortcut for converting kg to lbs: double the kilogram value and add 10 percent of the doubled number. For example, 80 kg: doubled is 160, plus 10 percent (16) equals 176 lbs. The exact answer is 176.37 lbs, so this trick is remarkably accurate. For pounds to kilograms, divide by 2 and subtract 10 percent: 200 lbs divided by 2 is 100, minus 10 percent (10) equals 90 kg. The exact answer is 90.72 kg.

Remember that there are exactly 1,000 grams in a kilogram, 1,000 milligrams in a gram, and 1,000 kilograms in a metric ton. The metric system's consistent decimal structure makes scaling between units simple. In contrast, the imperial system uses 16 ounces per pound and 14 pounds per stone, which requires more careful arithmetic.

A common mistake is confusing fluid ounces with weight ounces. A fluid ounce is a measure of volume, not weight. Eight fluid ounces of water weighs approximately 8.35 avoirdupois ounces because water is slightly denser than the reference used to define fluid ounces. For dry ingredients like flour or sugar, the weight of a fluid ounce varies significantly depending on the density of the substance. Always check whether a recipe specifies weight ounces or fluid ounces.

If you also need to convert length or area measurements, our length unit converter and area unit converter follow the same instant-conversion approach. For temperature conversions, check out our temperature conversion tool.

Common Weight Conversion Reference Values

The following table lists frequently needed weight equivalents for quick reference. These cover the most commonly searched conversions across cooking, fitness, shipping, and everyday life.

From	To	Value
1 ounce	Grams	28.3495 g
1 pound	Kilograms	0.453592 kg
1 stone	Kilograms	6.35029 kg
1 short ton	Kilograms	907.185 kg
1 gram	Ounces	0.035274 oz
1 kilogram	Pounds	2.20462 lbs
1 metric ton	Pounds	2,204.62 lbs
100 grams	Ounces	3.5274 oz
500 grams	Pounds	1.10231 lbs
5 kilograms	Pounds	11.0231 lbs
50 kilograms	Pounds	110.231 lbs
100 kilograms	Pounds	220.462 lbs

Frequently Asked Questions

How many pounds are in a kilogram?

One kilogram equals approximately 2.20462 pounds. This conversion factor is derived from the international pound agreement, which defines one pound as exactly 0.45359237 kilograms. To convert any kilogram value to pounds, simply multiply by 2.20462. For example, 50 kg equals 110.23 lbs, and 100 kg equals 220.46 lbs. This is one of the most commonly searched weight conversions worldwide.

What is the difference between mass and weight?

Mass is the amount of matter in an object and remains constant regardless of location. Weight is the gravitational force acting on that mass and varies depending on the strength of the local gravitational field. On Earth, a 70 kg object weighs approximately 686 newtons. On the Moon, the same 70 kg mass would weigh only about 114 newtons because lunar gravity is roughly one-sixth of Earth's. For everyday purposes on Earth, mass and weight are used interchangeably, and this converter treats them as equivalent.

What is the difference between a troy ounce and a regular ounce?

A troy ounce equals 31.1035 grams, while a regular (avoirdupois) ounce equals 28.3495 grams. Troy ounces are used exclusively for precious metals like gold, silver, and platinum. When you see gold priced at a certain amount per ounce, it always means troy ounces. A troy pound contains 12 troy ounces (373.24 grams), while an avoirdupois pound contains 16 avoirdupois ounces (453.59 grams). Confusing the two systems when trading precious metals can result in significant financial discrepancies.

How do I convert between metric tons, short tons, and long tons?

A metric ton (tonne) equals 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 1,016.05 kilograms. To convert metric tons to short tons, multiply by 1.10231. To convert metric tons to long tons, multiply by 0.984207. International shipping typically uses metric tons, US domestic freight uses short tons, and some older British industries still reference long tons. Always clarify which ton is meant in commercial contexts.

How many grams are in a cup of flour?

A cup of all-purpose flour weighs approximately 120 to 130 grams, depending on how it is measured. Sifted flour is lighter at around 120 grams per cup, while scooped and packed flour can weigh up to 150 grams. This variability is precisely why professional bakers prefer weighing ingredients in grams rather than measuring by volume. A kitchen scale that displays both grams and ounces eliminates guesswork and produces more consistent results in baking.

What does a stone weigh in pounds and kilograms?

One stone equals exactly 14 pounds or approximately 6.35029 kilograms. The stone is a traditional British unit still widely used in the United Kingdom and Ireland for expressing body weight. For example, a person who weighs 11 stone 4 pounds weighs 158 pounds or 71.67 kilograms. To convert stones and pounds to kilograms, first convert everything to pounds (stones × 14 + remaining pounds), then multiply by 0.453592. While the stone is not commonly used outside the UK, it appears frequently in British media, health guidelines, and casual conversation.

How accurate is this weight converter?

This converter uses IEEE 754 double-precision floating-point arithmetic, providing approximately 15 to 17 significant decimal digits of precision. The conversion factors are based on internationally standardized definitions — for example, one pound is defined as exactly 0.45359237 kilograms. For all practical applications including cooking, fitness tracking, shipping, and scientific work, the results are effectively exact. All calculations run entirely in your browser using JavaScript, with no server-side rounding or data transmission.

Why do some countries use kilograms and others use pounds?

The division stems from historical adoption of different measurement systems. France developed the metric system in the 1790s, and it spread across continental Europe, South America, and eventually most of the world through colonization, trade agreements, and scientific standardization. Britain and its colonies, including the American colonies, used the imperial system. While the United Kingdom has largely transitioned to metric for trade and science, it retains stones and pounds for body weight in casual use. The United States remains the most prominent holdout, using pounds for nearly all everyday weighing despite metric being the legal standard for trade since 1866.

How do I weigh luggage for airline travel?

Most international airlines specify luggage weight limits in kilograms — typically 23 kg for checked bags in economy class and 7 to 10 kg for carry-on bags. US domestic airlines often list limits in pounds — 50 lbs for checked bags. Since 23 kg equals 50.71 lbs and 50 lbs equals 22.68 kg, these limits are essentially equivalent. To avoid overweight baggage fees, weigh your luggage at home using a bathroom scale or a portable luggage scale. If your scale reads in pounds and the airline limit is in kilograms, use this mass converter to check your allowance precisely.

What are common mistakes when converting weight units?

The most frequent mistake is confusing the direction of conversion — multiplying when you should divide, or vice versa. When converting from a larger unit to a smaller unit, the number gets bigger (1 kg = 1,000 g), and when converting from smaller to larger, the number gets smaller (1,000 g = 1 kg). Another common error is mixing up troy ounces and avoirdupois ounces when dealing with precious metals. Additionally, people sometimes confuse fluid ounces (a volume measure) with weight ounces, which can lead to inaccurate recipe results. Always verify which unit system is being used before converting.

Can I use this converter for scientific measurements?

Yes. This weight converter provides sufficient precision for virtually all scientific applications. The conversion factors are based on internationally standardized definitions maintained by the International Bureau of Weights and Measures (BIPM). For laboratory work involving milligrams and micrograms, the metric system's decimal structure makes conversions straightforward — simply move the decimal point. For cross-system conversions between metric and imperial units, this tool uses the exact defined relationships, ensuring results that are accurate to the full precision of double-precision floating-point arithmetic.

Can I use this converter offline?

Yes. Because all calculations run in your browser using client-side JavaScript, the converter works without an internet connection once the page has loaded. No data is transmitted to any server during the conversion process. This makes it ideal for use in kitchens, gyms, warehouses, laboratories, and any situation where internet access may be limited. Simply bookmark this page for quick access anytime you need to convert between weight units including kg to lbs, grams to ounces, and stones to kilograms.