Mass Calculator
You can reach a mass two ways. Multiply a density by a volume, or divide a weight by the gravitational acceleration it was measured under. This calculator does both and gives the mass in kilograms, grams, pounds and ounces.
Find the mass from
Mass in kilograms (kg)
1
Mass in grams (g)
1,000
Mass in pounds (lb)
2.20462
Mass in ounces (oz)
35.274
Pick the place the weight was measured, or type your own g.
Mass in kilograms (kg)
10
Mass in grams (g)
10,000
Mass in pounds (lb)
22.0462
Mass in ounces (oz)
352.74
Conversions use exact definitions: 1 lb = 0.45359237 kg, 1 oz = 1/16 lb, 1 in = 2.54 cm, 1 US gallon = 231 in³, 1 L = 1,000 cm³, 1 kgf = 9.80665 N and 1 lbf = 4.4482216152605 N. Results are rounded to six significant figures. A result with more than six digits before the decimal point is rounded to the whole number.
Standard gravity, 9.80665 m/s², is the exact value in NIST's table of constants. The other g presets are the Gravity row of NASA's Planetary Fact Sheet, which gives one decimal. NASA states it at the equator, and at the 1 bar pressure level for Jupiter, Saturn, Uranus and Neptune. Both pages were opened on October 14, 2026.
How to use the Mass Calculator
- Pick what you know. "Density and volume" multiplies the two. "Weight and gravity" divides a force by g.
- For density and volume, type the density and pick its unit: kg/m³, g/cm³, kg/L, lb/ft³ or lb/in³. Then type the volume and pick m³, liters, cm³, ft³, in³ or US gallons. The two units do not have to match, because the calculator converts both.
- For weight and gravity, type the weight in newtons, pounds-force or kilograms-force. Pick the place it was measured to fill in g, or type your own g in m/s². The list has Earth at standard gravity, the Moon, the other seven planets and Pluto.
- Read the mass in kilograms, grams, pounds and ounces. The results update as you type, so there is no button to press.
The mass formulas
m = ρ × V m = W ÷ g
ρ is the density, V the volume, W the weight and g the gravitational acceleration. With ρ in kg/m³ and V in m³, ρ × V gives the mass in kilograms. With W in newtons and g in m/s², W ÷ g gives kilograms as well. The calculator converts every input to those units first, using exact definitions such as 1 lb = 0.45359237 kg, 1 in = 2.54 cm and 1 lbf = 4.4482216152605 N. Each result is rounded to six significant figures, or to the whole number when it has more than six digits before the decimal point. A mass above 10^18 kg or under 10^-18 kg gets a message, because it comes from a mistyped field.
Worked example
The fields start with these numbers, so you can check each result. A density of 2.5 g/cm³ and a volume of 400 cm³ give m = 2.5 × 400 = 1,000 g. The calculator shows 1 kg, 1,000 g, 2.20462 lb and 35.274 oz. Switch to weight and gravity. A weight of 98.0665 N at standard gravity, 9.80665 m/s², is m = 98.0665 ÷ 9.80665 = 10 kg, shown as 10 kg, 10,000 g, 22.0462 lb and 352.74 oz. Pick the Moon, where g is 1.6 m/s², and the same 98.0665 N comes from a mass of 61.2916 kg.
Frequently asked questions
What is the difference between mass and weight?
Mass is the amount of matter in an object, measured in kilograms. Weight is the force gravity puts on that mass, measured in newtons. Take an object to the Moon and its mass stays the same while its weight drops. That is why the weight mode asks for g. A weight of 98.0665 N means 10 kg at standard gravity and 61.2916 kg at the Moon's 1.6 m/s².
Is a pound a unit of mass or of force?
There is one of each. The pound, lb, is a mass of exactly 0.45359237 kg. The pound-force, lbf, is the weight of one pound at standard gravity, exactly 4.4482216152605 N. In this calculator a weight in lbf goes into the weight mode, and every result in pounds is a mass in lb. A weight of 22 lbf at standard gravity is a mass of 22 lb, or 9.97903 kg.
Can I mix units, such as lb/ft³ with liters?
Yes. The calculator turns the density into kg/m³ and the volume into m³ before it multiplies, so any pair works. A density of 62.4 lb/ft³ and a volume of 2 ft³ give 124.8 lb, which is 56.6083 kg. The same density with 50 liters gives 110.182 lb, which is 49.9776 kg.
Where do I find the density of a material?
Take it from a measurement or from the data sheet of the exact product. This page lists no material densities, because the figure changes with the alloy, the mix and the temperature. If you can weigh a sample and measure its volume, the density calculator gives ρ = m ÷ V.
Where do the g values in the list come from?
They are the same as on the weight calculator. Standard gravity, 9.80665 m/s², is the exact value NIST lists as the standard acceleration of gravity. The Moon, the planets and Pluto use the Gravity row of NASA's Planetary Fact Sheet, which gives one decimal, such as 1.6 for the Moon and 3.7 for Mars. Both pages were opened on October 14, 2026. If you know a more exact g, type it in.