This calculator can convert values between the common weight and mass units.
| Milky Way Galaxy | 1.15357 x 1042 kg or 5.8 x 1011 solar mass |
| Sun | 1.9891x1030 kg |
| Earth | 5.9736 x 1024 kg |
| Moon | 7.3477 x 1022 kg |
| Atomic Mass Unit (u) | 1.660539066(83) x 10-27 kg |
| Neutron | 1.67492729(28) x 10-27 kg or 1.0086649156(6) u |
| Proton | 1.672621637(83) x 10-27 kg or 1.00727646677(10) u |
| Electron | 9.10938215(45) x 10-31 kg or 5.4857990943(23)x10-4 u |
Early Babylonian and Egyptian records, as well as the Bible, indicate that weight was originally measured by the capacities of containers such as gourds or clay or metal vessels. These were filled with plant seeds that were then counted to measure the volumes. With the development of scales as a means of weighing, seeds and stones served as standards. For instance, the "carat," still used as a mass unit for gems, is derived from the carob seed.
The Babylonians invented the talent, as the basic unit of weight, and, based on their sexagesimal (60-based), divided into equal parts in terms of that number.
It was equal to the amount of water that filled an amphora (a kind of vase).
The Greeks used the same weight measurement as the Babylonians, but the Romans changed it. Their basic unit of weight was the 'uncia,' from which the English word 'ounce' is originally derived. The uncia is a twelfth part of the 'pes,' which is the Roman 'foot' — our word inch is also derived from 'uncia.' The Romans used the same word for ounce, which they measured using a technique taken from the Arabs.
For the Arabs, a silver Dirhem was determined by 45 full grown barley grains. Ten Dirhems made a Wukryeh of 450 grains, which we call an ounce from the Latin "uncia" or twelfth, which name is used genetically for such a class of weight or volume.
Translated into English as the 'ounce,' King Offa, who lived at the end of the 8th century, accepted the silver ounce but then ran short of silver. The Dirhem was halved to 222 grains for the penny, twenty of which made the ounce as before, and twelve ounces the pound in silver.
This measure has come down to us as part of the British Imperial System of Weights and Measures, which is also used in the U.S. This system of units was first defined in the British Weights and Measures Act of 1824, which was later refined and reduced. The system came into official use across the British Empire.
In 1855, a fire destroyed the Houses of Parliament in London, where the standards for these weights were kept. A standards bureau was set up with prototypes for the imperial system at that time.
Metric weights have a very different history. Metric weights, the gram, the kilogram, were developed by scientists in 18th century France. In 1791, the French parliament imposed the use of the metric system on the country, and it is now used in Continental Europe and many other parts of the world.
The metric system was not particularly popular in revolutionary France, and Emperor Napoleon, who came just after the Revolution, abolished it. But, when Napoleon lost power, the system was reinstated.
The kilogram is the weight of one liter of water. One thousandth of a kilogram is a gram. All multiples and submultiples of the base units are in powers of ten. Fractional units are not halves, but tenths, unlike the customary practice for fractions of inches, and derived units are related to the base units by multiples of powers of ten, unlike what is the case with twelve inches making a foot. Basing all units on multiples of ten makes conversion from one unit to another particularly easy.
Here are some typical metric conversions:
Although the terms weight and mass are often used interchangeably in everyday conversation, they have distinct scientific meanings. Understanding the difference is essential for accurate measurements and conversions.
Mass is the amount of matter in an object. It is a fundamental property that does not change regardless of location. An object with a mass of 10 kilograms on Earth will still have a mass of 10 kilograms on the Moon, in space, or anywhere else in the universe. Mass is measured in kilograms, grams, pounds-mass, and similar units. Our mass calculator can help with precise mass conversions.
Weight is the force exerted by gravity on an object's mass. Since gravity varies from place to place, weight is not constant. On Earth, the acceleration due to gravity is approximately 9.81 m/s², while on the Moon it is only 1.62 m/s². This means a person who weighs 180 pounds on Earth would weigh only about 30 pounds on the Moon, even though their mass has not changed.
In everyday life on Earth, weight and mass are proportional and the distinction is often unimportant. However, in scientific contexts, engineering, and space exploration, the difference is critical. Scales actually measure weight (the force), but are calibrated to display mass by assuming standard Earth gravity. This is why a spring scale gives different readings at the equator versus the poles, where gravity differs slightly. Our density calculator uses mass and volume to calculate density, which is independent of gravitational variations.
Converting between weight and mass units is straightforward once you know the conversion factors. Whether you are cooking, shipping packages, or working on scientific calculations, our weight converter makes the process simple. Understanding these conversions is essential in our interconnected world where different countries and industries use different measurement systems.
To convert pounds to kilograms, multiply by 0.45359237. For example, a 150-pound person weighs 150 × 0.45359237 = 68.04 kilograms. A 10-pound bag of potatoes weighs 4.54 kilograms. To convert ounces to grams, multiply by 28.3495. For instance, 8 ounces of cheese equals approximately 226.8 grams. These conversions are essential for international travel, medical dosages, and scientific research. If you also need to convert volume measurements, our volume calculator can help with related conversions between liters, gallons, and cubic meters.
To convert kilograms to pounds, multiply by 2.20462. For example, a 5-kilogram bag of flour weighs 5 × 2.20462 = 11.02 pounds. A 70-kilogram person weighs approximately 154.32 pounds. To convert grams to ounces, divide by 28.3495. For example, 500 grams of sugar equals about 17.64 ounces. These conversions are commonly used when following recipes, shipping goods internationally, or comparing product specifications. The precision of the conversion factor matters — using 2.2 instead of 2.20462 introduces a 0.2% error that can add up with larger numbers.
Metric conversions are simple because they are based on powers of ten. To convert from kilograms to grams, multiply by 1,000. To convert from grams to milligrams, multiply by 1,000. To convert from kilograms to metric tons, divide by 1,000. To convert from grams to micrograms, multiply by 1,000,000. The metric system's decimal nature makes it far easier to work with than imperial units for scientific and engineering applications. For example, converting 2.5 kilograms to milligrams is simply 2.5 × 1,000,000 = 2,500,000 milligrams — no complex fractions or memorized conversion factors needed.
Our weight calculator handles all these conversions automatically. Simply enter the value, select the source unit, select the target unit, and the result appears instantly. The calculator supports kilograms, grams, milligrams, tons, pounds, ounces, carats, atomic mass units, grains, US and UK quarters, and US and UK stones. This eliminates the need to memorize conversion factors and reduces the risk of calculation errors. For more complex calculations involving mass, volume, and density, try our density calculator which integrates these measurements seamlessly.
The two major systems for measuring weight and mass are the metric system and the imperial (US customary) system. Each has its advantages and is used in different parts of the world. Understanding both systems is essential for international communication, trade, and travel.
The metric system is used by over 95% of the world's population. Its base unit of mass is the kilogram, with prefixes like milli-, centi-, and kilo- indicating multiples of ten. The system was developed in France during the 18th century and is now the official system of measurement in most countries. One of the greatest advantages of the metric system is its consistency — converting between units simply requires moving the decimal point. For example, 1 kilogram = 1,000 grams = 1,000,000 milligrams. There is no need to memorize arbitrary conversion factors like 16 ounces per pound or 14 pounds per stone. The metric system's consistency makes it ideal for scientific work, international trade, and education. Our unit converter supports all metric prefixes and units for quick and accurate conversions.
The imperial system is primarily used in the United States and, to a lesser extent, in the United Kingdom and a few other countries. Its weight units include the pound (lb), ounce (oz), stone, and ton. The imperial system evolved over centuries from various historical measurement traditions, which is why its conversion factors are irregular. For example, there are 16 ounces in a pound, 14 pounds in a stone, and 2,000 pounds in a US ton. The UK (long) ton equals 2,240 pounds. These irregular conversions make the imperial system more challenging to work with, but it remains deeply ingrained in American culture, from body weight measured in pounds to food sold by the ounce. Many Americans have an intuitive understanding of pounds and ounces but find kilograms and grams unfamiliar.
The choice between systems depends on your location and field. If you are in the US, imperial units are standard for everyday use. For scientific work, international trade, and most professional fields, the metric system is preferred. Our weight calculator supports both systems, making it easy to convert between them regardless of which system you need. For professionals working in international contexts, being bilingual in both measurement systems is increasingly important. You may also find our density calculator useful when working with mass and volume measurements in either system, as it automatically handles unit conversions for you.
While there have been periodic efforts to convert the US to the metric system, change has been slow and expensive. The US officially adopted the metric system for trade and commerce in 1975 with the Metric Conversion Act, but the transition has been voluntary rather than mandatory. Today, many US industries use both systems — for example, soda is sold in 2-liter bottles (metric) while milk is sold in gallons (imperial). Understanding both systems and being able to convert between them remains an essential skill in our globalized world.
Weight and mass conversion is used in countless everyday situations. Understanding how to convert between units is a valuable skill in many fields, from professional environments to household tasks.
Recipes from different countries use different measurement systems. A European recipe might list ingredients in grams, while an American recipe uses cups and ounces. Accurate weight conversion ensures consistent results. For example, 250 grams of flour equals approximately 8.8 ounces. Professional bakers always use weight measurements for precision, as volume measurements can vary significantly depending on how ingredients are packed. A cup of flour can weigh anywhere from 120 to 150 grams depending on how it is scooped, while 120 grams is always 120 grams. This is why serious home bakers invest in a kitchen scale and learn to convert between ounces and grams.
Shipping companies charge based on package weight, and different countries use different units. International shipping requires converting between pounds and kilograms to calculate costs and meet regulatory requirements. A package weighing 22 pounds equals 10 kilograms, and knowing this conversion is essential for accurate shipping label preparation. Freight companies typically use kilograms for international shipments and pounds for domestic US shipments. Misunderstanding these units can lead to incorrect postage, delayed deliveries, or additional fees. Our weight calculator ensures you always use the correct values when preparing shipments.
Body weight is measured in pounds in the US and kilograms in most other countries. Fitness enthusiasts and travelers often need to convert between these units. Many fitness apps allow you to switch between units, but understanding the conversion helps you track progress regardless of the scale you use. A weight loss goal of 10 pounds is equivalent to 4.54 kilograms. Our BMI calculator accepts weight in both pounds and kilograms, making it accessible regardless of your preferred unit system.
Medical dosages are typically calculated in milligrams per kilogram of body weight, requiring precise conversion between units. Scientific research uses the metric system exclusively, but equipment from different sources may display measurements in different units, making conversion skills essential. Pharmacists regularly convert between grams, milligrams, and micrograms when preparing medications. Our mass calculator provides the precision needed for scientific and medical applications, and our unit converter supports all the units used in healthcare and laboratory settings.
Avoid these common errors when converting between weight and mass units to ensure accuracy in your calculations. Being aware of these pitfalls will help you get reliable results every time.
The most fundamental error is treating weight and mass as identical. While they are proportional on Earth, they are fundamentally different physical quantities. Mass is constant; weight varies with gravity. In most everyday contexts, the distinction is negligible, but in scientific and engineering work, it matters significantly. For example, a satellite's mass determines its orbital mechanics, while its weight is essentially zero in free fall. Always consider whether your application requires mass or weight, and choose the appropriate units and measurement method.
Many people use approximate conversion factors when exact ones are needed. For example, using 2.2 instead of 2.20462 for kilograms to pounds can introduce errors, especially with large numbers. For precise work, always use the exact conversion factors provided in our weight converter. A 0.2% error might seem small, but when converting 1,000 kilograms, the difference between 2,200 and 2,204.62 pounds is 4.62 pounds — enough to matter in shipping and manufacturing. Our unit converter uses precise conversion factors for all supported units to eliminate this potential source of error.
A US ton (2,000 pounds) is different from a UK ton (2,240 pounds). Similarly, US and UK quarts and gallons differ. When converting weights that involve these units, be sure to use the correct version. The difference of 240 pounds per ton can lead to significant errors in shipping and industrial applications. Our weight calculator clearly distinguishes between US and UK variants of units like quarters and tons, displaying both options so you can select the correct one for your needs.
When a calculation involves multiple measurements, ensure all are in the same unit system before proceeding. Mixing kilograms and pounds in a single calculation will produce incorrect results. This is especially common in recipes when some ingredients are measured in cups and others in grams, or in engineering when specifications from different countries use different units. Use our weight calculator to convert all values to a consistent unit before performing calculations with other tools like our density calculator or volume calculator, which assume consistent unit inputs.
Rounding intermediate results before the final calculation can introduce significant errors. Always keep full precision throughout your calculations and round only the final result to the appropriate number of significant figures. Our weight calculator handles this automatically, maintaining full precision internally and displaying results with appropriate formatting based on the magnitude of the value.
Follow these tips to ensure accurate weight and mass conversions every time, whether you are working in a professional laboratory or cooking in your home kitchen.
Familiarize yourself with the units you are converting between. Understand whether you are working with avoirdupois (standard) ounces or troy ounces, US or UK tons, and short or long hundredweights. Using the wrong variant can lead to significant errors. For example, a troy ounce (used for gold) is 31.1 grams, while a standard ounce is 28.35 grams — a difference of nearly 10%. When buying or selling precious metals, this distinction is critical.
For the most accurate results, use exact conversion factors rather than approximations. The exact conversion from pounds to kilograms is 0.45359237, not simply 0.45. Our weight converter uses precise factors for all supported units, ensuring reliable results down to the last decimal place. This level of precision is essential for pharmaceutical compounding, scientific research, and industrial quality control where small errors can have significant consequences.
When converting manually, verify your calculation by converting back to the original unit. For example, if you convert 10 pounds to kilograms, convert the result back to pounds to confirm accuracy. This simple check catches most conversion errors. Our weight calculator eliminates the need for manual verification because it performs all conversions with maximum precision and consistency.
The precision of your result should match the precision of your input. If you measure something as 5 pounds (one significant figure), reporting the result as 2.26796 kilograms implies more precision than you actually have. Round appropriately to avoid false precision. In general, your result should have no more significant figures than your least precise input measurement.
For professional or critical applications, always use a reliable conversion tool. Our weight calculator provides precise conversions across all common weight and mass units, from the largest (tons) to the smallest (atomic mass units). For related calculations, our density calculator and mass calculator use the same high-precision conversion factors and are designed to work seamlessly together for complex multi-step calculations.
Weight and mass conversion is a fundamental skill that applies to countless aspects of daily life, from cooking and shipping to science and medicine. Whether you are a student learning about measurement systems, a professional working with international standards, or someone who simply wants to follow a recipe from another country, understanding how to convert between weight units is essential.
Our free weight calculator simplifies the conversion process by supporting both imperial and metric units, including kilograms, pounds, ounces, grams, milligrams, tons, carats, and more specialized units like atomic mass units, grains, quarters, and stones. The calculator provides instant, accurate results with just a few clicks, eliminating the need to memorize conversion factors or perform manual calculations that are prone to error.
We encourage you to explore our other related tools to expand your measurement capabilities. Try our unit converter for all types of measurement conversions including length, temperature, area, and volume. Use our density calculator to explore the relationship between mass and volume, and our volume calculator for volume-related calculations. For health and fitness applications, our BMI calculator and body fat calculator both use weight inputs and support multiple unit systems, making them accessible whether you think in pounds or kilograms.
Understanding weight and mass conversions is more than just a practical skill — it is a window into the fascinating history of human civilization and trade. From ancient Babylonian talents to modern atomic mass units, the way we measure weight tells the story of our species' journey from local barter to global commerce. Bookmark this page and come back whenever you need to perform weight conversions. If you found this tool helpful, please share it with others who might benefit from quick and accurate weight and mass unit conversions. With practice, converting between pounds and kilograms will become second nature, saving you time and ensuring accuracy in all your measurement tasks.
To learn more about weight calculator, visit Mayo Clinic.
To convert pounds to kilograms, multiply the number of pounds by 0.45359237. For example, 10 pounds equals approximately 4.54 kilograms. Our weight calculator does this conversion instantly and supports both US and UK units.
There are 16 ounces in a pound (avoirdupois weight). This is part of the US customary system of measurement. The pound and ounce have been used for centuries in English-speaking countries.
A US quarter (quarter [US]) equals 25 pounds (or about 11.34 kg). A UK quarter (quarter [UK]) equals 28 pounds (or about 12.70 kg). The UK quarter is based on the imperial hundredweight of 112 pounds.
The stone is primarily used in the UK and Ireland to measure body weight. One stone equals 14 pounds (approximately 6.35 kg). It is commonly used when discussing personal weight in these countries.
One ounce (avoirdupois) equals approximately 28.35 grams. The troy ounce, used for precious metals like gold and silver, equals about 31.1 grams. Always check which ounce system you are using for accurate conversions.
Mass is the amount of matter in an object and remains constant regardless of location. Weight is the force exerted by gravity on that mass. On Earth, they are often used interchangeably, but on the Moon, your weight would be one-sixth of what it is on Earth while your mass stays the same.
To convert kilograms to pounds, multiply the number of kilograms by 2.20462. For example, 5 kilograms equals approximately 11.02 pounds. Our weight calculator can instantly convert between these and many other units.
A metric ton (tonne) equals 1,000 kilograms or approximately 2,204.62 pounds. It is the standard unit for measuring large masses in most countries. The short ton (US) equals 2,000 pounds, while the long ton (UK) equals 2,240 pounds.
There are 1,000 milligrams in a gram. The milligram is commonly used in medicine and pharmacology for precise dosage measurements. Our weight converter handles all metric prefixes automatically for accurate results.
A carat is a unit of mass used for gemstones and pearls, equal to 200 milligrams or 0.2 grams. The word carat comes from the carob seed, which was historically used as a standard for weighing precious stones.
To convert ounces to grams, multiply the number of ounces by 28.3495. For example, 8 ounces of flour equals approximately 226.8 grams. This conversion is essential in cooking when following recipes from different countries.
The US customary system, including pounds, originated from the British Imperial System. While most countries adopted the metric system for its simplicity, the US continues to use customary units due to historical precedent, infrastructure costs, and cultural familiarity with the existing system.