Weight Converter for kg, lb, oz, Stone and Tonnes
Convert a nonnegative mass between metric, avoirdupois, troy and selected jewellery units. These are often called weight units in everyday use. The calculator keeps every stated factor exact and shows each conversion through kilograms.
- 26 mass units
- Exact rational factors
- Regular vs troy ounces
- Metric, US and UK tons
Online Weight Converter
Enter one mass, choose the source and target units, then set the displayed significant digits. The full table converts the same mass into all 26 supported units.
Weight conversion result
1 kg ≈ 2.204622622 lb.
All Supported Weight Units
| Unit | Symbol or UI label | Converted value | Display relation |
|---|
Calculation Steps
How to Use This Weight Converter
- Enter the mass. Type a nonnegative decimal or scientific-notation value without commas or a unit suffix.
- Choose the source unit. Select the unit attached to the value, including the correct ounce, hundredweight or ton family.
- Choose the target unit. Select the unit in which you want the same physical mass reported.
- Set the precision. Choose how many significant digits the displayed results should retain.
- Convert the value. Review the answer, kilogram normalization, factor basis and calculation steps.
- Check the full table. Compare the same mass across all 26 supported units, then round for your measurement or task.
The Swap Units button reverses the selected pair without changing the entered number. It does not reuse a previously rounded answer. This protects the conversion from extra rounding error when you switch direction.
Weight Conversion Formula
Each supported unit has an exact factor that expresses one unit in kilograms. The calculator first normalizes the entered mass to kilograms, then divides by the target unit's kilogram factor.
For example, one avoirdupois pound equals exactly 0.45359237 kilogram. To convert 75 kilograms to pounds:
Rounded to two decimal places, the result is 165.35 lb. The physical mass stays the same. Only the numerical value and unit change. Keep the exact factor during the calculation and round the final result once.
Exact Unit Definitions Used
The kilogram is the SI base unit of mass. SI prefixes create exact decimal multiples and submultiples. The international avoirdupois pound is exactly 0.45359237 kg, which makes the ordinary ounce, grain and related units exact through their stated ratios.
| Unit | Kilogram relationship | Definition used |
|---|---|---|
| Gram | 1 g = 0.001 kg | Exact SI relationship |
| Metric carat | 1 ct = 0.0002 kg | Exactly 200 mg |
| Avoirdupois pound | 1 lb = 0.45359237 kg | Exact international definition |
| Avoirdupois ounce | 1 oz = 0.028349523125 kg | Exactly 1/16 lb |
| Grain | 1 gr = 0.00006479891 kg | Exactly 1/7000 lb |
| Stone | 1 st = 6.35029318 kg | Exactly 14 lb |
| US short ton | 1 ton (US) = 907.18474 kg | Exactly 2000 lb |
| Imperial long ton | 1 ton (UK) = 1016.0469088 kg | Exactly 2240 lb |
| Troy ounce | 1 oz t = 0.0311034768 kg | Exactly 480 grains |
| Troy pound | 1 lb t = 0.3732417216 kg | Exactly 12 troy ounces |
| Standard tola | 1 tola = 0.0116638038 kg | Historical 180-grain convention |
| Tonne | 1 t = 1000 kg | Exact metric relationship |
The converter labels every ambiguous unit family. It never treats an unqualified ounce, hundredweight or ton as interchangeable with another unit carrying the same general name.
Mass Versus Physical Weight-Force
People often say an object "weighs 75 kg." In precise physics language, 75 kg is its mass. Mass describes inertia and does not change merely because the object moves from Earth to the Moon. Weight is a force caused by gravity and is measured in newtons.
At conventional standard gravity, g0 is exactly 9.80665 m/s2. A 1 kg mass therefore corresponds to 9.80665 N of standard weight-force. Local gravity differs by location and altitude. This page does not calculate newtons, pound-force or kilogram-force. Use the Force Calculator when force is the required quantity.
Regular Ounces, Troy Ounces and Carats
The ordinary ounce used for body weight, food and many goods is the avoirdupois ounce. It is exactly 1/16 avoirdupois pound, or 28.349523125 grams. The troy ounce used for precious metals is exactly 480 grains, or 31.1034768 grams. A troy ounce is therefore heavier than an avoirdupois ounce.
The troy pound contains 12 troy ounces, while the avoirdupois pound contains 16 avoirdupois ounces. The two pounds are not equal. A troy pound is about 373.24 grams, while an avoirdupois pound is exactly 453.59237 grams.
A metric carat is a mass of exactly 200 milligrams. It is used for gemstones. Carat does not mean karat: karat describes gold fineness as parts out of 24 and is not a mass unit. Fluid ounces measure volume and do not belong in this calculator.
Tonne, Short Ton, Long Ton and Hundredweight
A tonne, also called a metric ton, equals exactly 1000 kg. A US short ton equals exactly 2000 avoirdupois pounds, or 907.18474 kg. An Imperial long ton equals exactly 2240 pounds, or 1016.0469088 kg. The difference is large enough to matter in freight, commodities, engineering and reporting.
Hundredweight also has two definitions. The US short hundredweight is 100 lb. The Imperial long hundredweight is 112 lb. A British quarter is 28 lb, so four quarters make one long hundredweight. The interface adds US or UK to these labels instead of guessing from your location.
Metric quintal means exactly 100 kg. It is common in agricultural and commodity contexts in several countries. Confirm the named unit in a contract, invoice, historical record or dataset before converting a bare value marked only as "ton" or "cwt."
Tola Convention Used by This Calculator
This page includes one explicitly labelled standard tola based on the historical 180-grain relationship. With the modern international grain, it equals exactly 11.6638038 grams. The value also equals 3/8 of a troy ounce.
Tola has a long South Asian history, but modern Indian legal metrology and formal trade use metric units. Local jewellery quotations or older records may use a stated house, regional or historical convention. Confirm the source definition before relying on a tola conversion for a sale, assay, inventory or legal document.
Accuracy, Significant Digits and Limits
An exact unit factor does not make the original measurement exact. A scale reading of 70 kg may be rounded to the nearest kilogram, while a laboratory balance may support several decimal places. Choose displayed digits that fit the source instrument and purpose.
The calculator parses the entered decimal as an exact rational number and applies every unit factor with BigInt rational arithmetic. It rounds only for display, using round-half-to-even at the selected significant-digit count. A rounded decimal receives an approximate sign. Zero remains exactly zero, and tiny nonzero results stay in scientific notation instead of becoming zero.
Inputs may contain up to 80 significant digits and a scientific exponent from −3000 through 3000. The tool rejects negative mass, commas, fractions, unit suffixes, incomplete exponents, Infinity and nonnumeric text. Real measurements may still include scale calibration, tare, buoyancy, moisture, packaging and sampling uncertainty.
Common Weight Conversion Mistakes
- Treating kilograms as force or converting kg directly to newtons without a gravitational acceleration.
- Mixing pounds of mass, lb, with pound-force, lbf.
- Using the ordinary ounce factor for a troy ounce of precious metal.
- Confusing an ounce of mass with a fluid ounce of volume.
- Leaving ton or hundredweight unqualified when US and Imperial definitions differ.
- Confusing metric carat mass with karat gold purity.
- Using a rounded shortcut such as 1 kg = 2.2 lb inside a multi-step calculation.
- Rounding the kilogram intermediate and then converting it again.
- Reading a decimal stone value as mixed stone-and-pound notation.
- Copying more displayed digits than the source scale supports.
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Weight Converter FAQs
What does this weight converter calculate?
It converts nonnegative mass values between metric, avoirdupois, troy, carat and the stated tola units. It does not convert force units such as newtons or pound-force.
Is weight the same as mass?
Everyday language often uses the words as synonyms. In physics, mass is measured in kilograms, while gravitational weight is a force measured in newtons.
How many pounds are in one kilogram?
One kilogram equals approximately 2.20462262185 avoirdupois pounds. The decimal repeats because the exact pound definition is 0.45359237 kilogram.
How many kilograms are in one pound?
One international avoirdupois pound equals exactly 0.45359237 kilogram.
How many ounces are in one pound?
One avoirdupois pound contains exactly 16 avoirdupois ounces.
How many pounds are in one stone?
One stone equals exactly 14 avoirdupois pounds, or exactly 6.35029318 kilograms.
Is a tonne the same as a US ton?
No. A tonne is exactly 1000 kg, while a US short ton is exactly 907.18474 kg. An Imperial long ton is exactly 1016.0469088 kg.
Is a troy ounce the same as a regular ounce?
No. A troy ounce is exactly 31.1034768 grams. A regular avoirdupois ounce is exactly 28.349523125 grams.
How many grams are in one tola?
Under the stated 180-grain historical convention, one tola equals exactly 11.6638038 grams. Modern trade should follow applicable metric and legal-metrology rules.
Does an object's weight change on the Moon?
The object's mass stays unchanged. Its gravitational weight-force changes because local gravitational acceleration is lower on the Moon.
Method and Review Basis
The kilogram, SI prefixes, tonne and distinction between mass and force were checked against the BIPM SI Brochure, 9th edition and NIST SI Units: Mass. Avoirdupois, troy, stone, hundredweight, ton and metric-carat relationships were checked against NIST Handbook 44, 2026, Appendix C. The international-pound basis was cross-checked against the NIST Guide to the SI, Appendix C. The historical 180-grain tola relationship was checked against the Standards of Weight Act, 1939 archive.
Measurement disclaimer: This calculator converts user-entered values using the stated mass-unit definitions. It does not certify a scale, tare, shipment, assay, medical measurement, commodity quantity or legal-metrology result. Verify the unit family, source precision and governing standard before consequential use.