Mass Calculator
- Updated
- Formula shown
- Free, no sign-up
Results
40.84 lb of structural steel (24 × 12 × 0.5 in)
- Water (20 °C)
- 5.193 lb
- Aluminum
- 14.05 lb
- Structural steel
- 40.84 lb
- Copper
- 46.61 lb
- Lead
- 58.79 lb
- Gold
- 100.4 lb
Mass is the amount of matter and is the same anywhere. Weight is the pull of gravity on that mass, so it changes from place to place: the same object weighs about a sixth as much on the Moon.
How to use the mass calculator
- Choose a substance from the list, or choose "Other" and type the density of your material in any unit.
- Enter the size: either the volume directly, or the dimensions of a rectangular block, a cylinder (rod, tube without the hole, disc) or a sphere.
- Add the number of identical pieces if you have more than one, and pick the unit for the answer.
- The bar chart shows what the same size would weigh in water, aluminum, steel, copper, lead and gold.
Mass formula
Block: V = L × W × H
Cylinder: V = π × d² × h ÷ 4
Sphere: V = π × d³ ÷ 6
Weight: W = m × g
Mass (m) equals density (ρ) times volume (V). The calculator converts every input to SI units first, so the density is in kg/m³ and the volume in m³, and the mass comes out in kilograms before being shown in your chosen unit. For a cylinder, d is the diameter and h the height or length; for a sphere, d is the diameter. The last line, W = m × g, turns mass into weight using standard gravity, g = 9.80665 m/s².
Worked examples
- Steel plate: a plate 24 × 12 × ½ inches has a volume of 144 in³ (0.00236 m³). With structural steel at 7,850 kg/m³, its mass is 18.52 kg, or 40.8 lb.
- Aluminum rod: a rod 5 cm in diameter and 1 m long holds π × 0.05² × 1 ÷ 4 = 0.001963 m³ (1.96 L). At 2,700 kg/m³, that is 5.3 kg (11.7 lb), which weighs 52 N on Earth.
Mass of common volumes
Calculated with the same engine from the density table on the density calculator page (sources and temperatures listed there).
| Substance | 1 liter (kg) | 1 ft³ (lb) | 1 US gallon (lb) |
|---|---|---|---|
| Water (20 °C) | 0.9982 | 62.32 | 8.33 |
| Ethanol (20 °C) | 0.7893 | 49.27 | 6.587 |
| Ice (0 °C) | 0.9167 | 57.23 | 7.65 |
| Polyethylene | 0.93 | 58.06 | 7.761 |
| Concrete (ordinary) | 2.3 | 143.6 | 19.19 |
| Aluminum | 2.7 | 168.6 | 22.53 |
| Structural steel | 7.85 | 490.1 | 65.51 |
| Copper | 8.96 | 559.4 | 74.77 |
| Lead | 11.3 | 705.4 | 94.3 |
| Gold | 19.3 | 1,205 | 161.1 |
Mass versus weight
In everyday speech the two words mean the same thing, but in science they don't. Mass is the amount of matter in an object, measured in kilograms or pounds (strictly, pounds-mass). It doesn't change if you take the object to the Moon. Weight is a force: the pull of gravity on that mass, measured in newtons or pounds-force. One kilogram weighs 9.80665 N at standard gravity, and one pound-mass weighs exactly one pound-force there, which is 4.4482 N.
A bathroom or kitchen scale actually measures force, then divides by Earth's gravity to display a mass. That is why the same scale would show a much smaller number on the Moon even though you would have exactly the same mass. To see how weight changes from planet to planet, use the weight calculator.
Tips for accurate results
- Use the right density. Alloys, wood species and plastics vary. If you have a datasheet value for your exact material, choose "Other" and type it in.
- Hollow parts: for a tube, work out the outer cylinder and the hole separately and subtract the masses.
- Loose materials such as sand or gravel need a bulk density that includes the air between grains, which is much lower than the solid density.
- Watch mixed units. Dimensions all use the length unit you choose, so enter every dimension in that unit.
Need the density instead? Measure mass and volume and use the density calculator. To count moles from a mass, the molecular weight calculator gives the molar mass of any chemical formula.
Frequently asked questions
How do you calculate mass from density and volume?
Multiply them: m = ρ × V, with both in matching units. A structural steel plate 24 × 12 × ½ in has a volume of 144 in³ (0.002360 m³); at 7,850 kg/m³ its mass is about 18.52 kg, or 40.8 lb.
How do I find the mass of a cylinder or rod?
Find the volume with V = π × d² × h ÷ 4, then multiply by the density. An aluminum rod 5 cm across and 1 m long has a volume of about 1.963 liters, so at 2,700 kg/m³ it has a mass of about 5.30 kg.
What is the difference between mass and weight?
Mass is the amount of matter and is measured in kilograms or pounds; it is the same everywhere. Weight is the force of gravity on that mass, measured in newtons or pounds-force. At standard gravity, 1 kg weighs 9.80665 N.
How much does a gallon of water weigh?
A US gallon of water at 20 °C has a mass of about 8.33 lb (3.78 kg). A liter of water at the same temperature is about 0.998 kg, and a cubic foot is about 62.3 lb.
Is a kilogram heavier on the Moon?
No. A kilogram is still a kilogram of matter on the Moon, but the Moon pulls on it with only about 1.6 N instead of about 9.8 N on Earth, so it weighs about a sixth as much.