Complete guide
Density Calculator: formulas, units and examples
Density is mass divided by volume: ρ = m/V. Enter any two quantities, choose the third under “Solve for,” and the calculator converts every value through SI units before returning the result in your selected unit.
How to calculate density
Measure the object's mass and the volume it occupies. Convert both measurements to compatible units, divide mass by volume, and attach a mass-per-volume unit to the answer.
For example, 8.9 kilograms divided by 0.001 cubic meter equals 8,900 kilograms per cubic meter. The same density can be written as 8.9 grams per cubic centimeter after converting both parts of the unit.
- Select Density under “Solve for.”
- Enter the measured mass and choose its unit.
- Enter the measured volume and choose its unit.
- Read the converted density and check the calculation breakdown.
The density equation and all three forms
NIST defines mass density as the mass of a substance divided by its volume. The symbol ρ is the Greek letter rho; m represents mass and V represents volume.
The same relationship solves three different questions. Use ρ = m/V for density, m = ρV for mass, and V = m/ρ for volume. Calculator24 exposes all three modes on one canonical page so the result follows the equation instead of forcing separate tools.
ρ = m ÷ Vm = ρ × VV = m ÷ ρHow to find mass from density and volume
Multiply density by volume after making the units compatible. A liquid with density 1.2 g/mL occupying 250 mL has a mass of 300 g. Select Mass, keep density in g/mL and volume in mL, then choose grams as the output unit.
How to find volume from mass and density
Divide mass by density. If a sample has a mass of 540 g and a density of 2.7 g/cm³, its volume is 200 cm³. Volume must be greater than zero when solving for density, and density must be greater than zero when solving for volume.
Units and dimensional analysis
The SI unit for mass density is kilograms per cubic meter (kg/m³). Laboratory work often uses g/cm³ or g/mL; US construction and material specifications may use lb/ft³ or lb/in³. A correct numerical operation can still produce a wrong answer if mass and volume units are mixed without conversion.
Calculator24 converts the inputs to kilograms and cubic meters internally, performs the selected equation, and converts only the final value to the requested unit. This keeps combinations such as pounds with liters or grams with cubic inches consistent.
Measuring the density of a real object
For a regular solid, measure its dimensions and calculate volume from its geometry. For an irregular solid that does not absorb or react with the liquid, volume can be estimated by displacement: subtract the initial liquid reading from the reading after full submersion.
Use a calibrated balance for mass, read liquid volume at eye level, and record temperature when precision matters. Water is often rounded to 1 g/mL, but USGS data show that its density changes with temperature and dissolved material.
Average density and practical limits
The result is an average density across the measured sample. Hollow objects, porous materials, mixtures and layered objects can have an average density that differs substantially from the density of each component.
Temperature and pressure affect volume and therefore density. The effect is usually modest for many solids and liquids over a small temperature range, but it can be large for gases. Match the conditions used by a reference table before identifying an unknown material from density alone.
Common density units
| Unit | Symbol | Equivalent in kg/m³ |
|---|---|---|
| Kilogram per cubic meter | kg/m³ | 1 |
| Gram per liter | g/L | 1 |
| Gram per milliliter | g/mL | 1,000 |
| Gram per cubic centimeter | g/cm³ | 1,000 |
| Pound per cubic foot | lb/ft³ | 16.01846 |
| Pound per US gallon | lb/gal | 119.8264 |
| Pound per cubic inch | lb/in³ | 27,679.90 |
Frequently asked questions
What is the formula for density?
Density equals mass divided by volume: ρ = m/V. In SI units, mass is in kilograms, volume is in cubic meters and density is in kg/m³.
How do you find volume with density and mass?
Divide mass by density: V = m/ρ. Convert the mass and density to compatible units first, or choose their units in this calculator.
How do you find mass with density and volume?
Multiply density by volume: m = ρV. The density's volume unit must correspond to the volume measurement.
Are g/mL and g/cm³ the same?
Yes. One milliliter is exactly one cubic centimeter, so 1 g/mL equals 1 g/cm³ and 1,000 kg/m³.
Why does water density change?
Temperature changes the space between water molecules, and dissolved substances also affect mass per unit volume. Use the temperature and composition stated by your reference source.
Is density the same as weight?
No. Density is mass per volume. Weight is a force caused by gravity. Everyday speech often uses weight for mass, but scientific calculations distinguish them.
What to keep in mind
Density can change with temperature and pressure. Keep the conditions and measurement precision in mind when comparing a calculated value with a reference value.
Results display up to 8 decimal places; exported numbers preserve calculation precision. This is a calculation summary, not an official certificate.