Weight and mass converter
Convert kilograms, grams, pounds, ounces, stones and metric tonnes.
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How it works
Convert mass between metric units, avoirdupois pounds and ounces, stones and explicitly labeled ton definitions. The table provides equivalents for the same physical mass and can be downloaded as CSV.
A few things to know
Mass conversion only, even though everyday language calls it weight. It does not convert force, density or volume. Ounces are avoirdupois mass ounces, not troy ounces or fluid ounces. Negative masses are rejected. Display uses up to 12 significant digits; this is not arbitrary-precision arithmetic or a measurement calibration. Numeric magnitude is bounded to 1e100, with nonzero inputs at least 1e-100.
When to use this tool
Packaging, shipping and everyday measurements often describe the same mass in different units. This weight and mass converter translates between metric masses, avoirdupois pounds and ounces, stones and three explicitly named ton definitions. It converts the amount of mass, without applying gravity or changing it into force. Enter a single number and select the original unit carefully: a fluid ounce, troy ounce and ordinary mass ounce are different quantities and are not interchangeable.
- Compare a product’s pound-based mass with a kilogram specification.
- Translate a shipment amount while keeping metric tonnes, short tons and long tons distinct.
- Create an equivalent-mass reference table for a scale reading or recorded item weight.
How to use weight and mass converter
Enter the mass reading
Place the numeric reading in Value without a suffix. If the source uses a compound stone-and-pound expression, combine it into one unit before entry.
Choose the exact source definition
Select From unit. Pounds and ounces mean avoirdupois mass, while ton choices explicitly state metric, US short or Imperial long.
Convert and compare
Set To unit and calculate. Read Converted value and the other equivalents in the table; download them if needed for your records.
Ten pounds expressed in kilograms
Inputs
Value 10; From unit Avoirdupois pounds (lb); To unit Kilograms (kg).
Result
Converted value is 4.5359237 kilograms. The table also shows 160 avoirdupois ounces and 4,535.9237 grams.
What it means
Each avoirdupois pound is 0.45359237 kilogram. Multiplying that definition by ten changes the numerical expression of the mass, without estimating shipping cost or applying a force calculation.
Common mistakes to avoid
Choosing an unspecified ton
A tonne, a 2,000-pound short ton and a 2,240-pound long ton differ. Confirm the source’s unit before conversion.
Treating a fluid ounce as a mass ounce
Fluid ounces measure volume. A conversion to mass requires the substance’s density and cannot be inferred from this tool.
Using avoirdupois for precious-metal units
Troy ounces are excluded. Do not select the ordinary ounce option for a source that specifies a troy ounce.
Frequently asked questions
Definitions, edge cases, and practical next steps for this tool. Search all tool FAQs ↗
How are mass values converted?
The calculator multiplies the input by the source unit’s kilogram factor and divides by the destination factor. Metric units use decimal scaling. Avoirdupois units are related through the international pound, with an ounce equal to one-sixteenth of that pound.
Does weight mean the same thing as mass here?
The title uses everyday wording, but the calculation converts mass. Physical weight as force depends on gravitational acceleration and is expressed in force units. No gravity value is entered and no newtons or pounds-force are calculated.
How many pounds are in a stone?
The stone option is defined as 14 avoirdupois pounds. If a source says 10 stone 5 pounds, first enter 145 pounds or 10 + 5/14 stones. Decimal 10.5 stones instead means ten and a half stones.
What distinguishes the three ton choices?
A metric tonne is 1,000 kilograms. A US short ton is 2,000 avoirdupois pounds, and an Imperial long ton is 2,240 pounds. Their labels include the definition so no regional meaning is silently selected for an ambiguous ton.
Can this convert grams into milliliters?
No. Grams are mass and milliliters are volume. A particular material’s density is needed to relate them. Temperature, composition and packing can affect that density, so a unit conversion alone cannot supply a universal grams-to-volume result.
Are ounces in this tool troy ounces?
No. They are avoirdupois ounces of 0.028349523125 kilogram. The tool excludes troy units and fluid units. If the original quantity is stated only as oz, check its context and source rather than assuming all ounce definitions are equivalent.
Can I convert zero or fractional masses?
Zero and nonnegative decimal values are supported. Negative values are rejected. A fraction should be entered as its decimal equivalent, because the numeric field does not parse text fractions such as 1/2 or arithmetic expressions.
How much precision does the result provide?
Outputs show up to 12 significant digits using floating-point arithmetic. A fixed conversion factor does not improve the accuracy of a scale reading. Round a converted measurement according to the original measurement’s useful precision and your practical task.
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Sources and method
Use the references below to check definitions and platform guidance. The model’s scope and limits are explained above. Read our editorial standards.