Density Calculator
Choose what you need — density, mass or volume — enter the other two in any units, and get the answer with the working, the density in nine units, and a check against common materials. Pick a fluid to see whether the object sinks or floats. Free, no sign-up.
Results
2.70 g/cm³
Density
54.0 g
Mass
20.0 cm³
Volume
2.70
Specific gravity (water at 4 °C = 1)
Close to Aluminum (2.7 g/mL). Density alone cannot identify a material: alloys, porosity and temperature all shift it.
It sinks in Water (20 °C).
Object 2.70 g/mL against fluid 0.9982 g/mL.
The working
ρ = m ÷ V
ρ = 54.0 g ÷ 20.0 mL = 2.700 g/mL
The density in other units
| Unit | Value |
|---|---|
| g/mL | 2.70 |
| g/cm³ | 2.70 |
| kg/L | 2.70 |
| g/L | 2700 |
| mg/mL | 2700 |
| kg/m³ | 2700 |
| lb/ft³ | 169 |
| lb/in³ | 0.0975 |
| lb/gal (US) | 22.5 |
Reference densities
| Material | g/mL (g/cm³) | kg/m³ |
|---|---|---|
| Air (dry) | 0.001204 | 1.204 |
| Ethanol | 0.7893 | 789.3 |
| Ice (0 °C) | 0.917 | 917 |
| Water (20 °C) | 0.9982 | 998.2 |
| Seawater | 1.025 | 1025 |
| Glycerol | 1.261 | 1261 |
| Aluminum | 2.7 | 2700 |
| Iron | 7.87 | 7870 |
| Copper | 8.96 | 8960 |
| Silver | 10.5 | 10500 |
| Lead | 11.3 | 11300 |
| Mercury | 13.55 | 13550 |
| Gold | 19.3 | 19300 |
Typical values near 20 °C from the CRC Handbook of Chemistry and Physics; seawater is approximate (35 g/kg salinity) and air is dry air at 101.325 kPa. Real samples vary.
How to Use the Density Calculator
- 1. Choose the unknown. Density, mass or volume.
- 2. Enter the other two with their units. Mass in µg to pounds, volume in µL to cubic feet and US gallons, density in g/mL, kg/m³, lb/ft³ and more. The answer is shown in the unit you pick beside it.
- 3. Optionally pick a fluid. The calculator compares the object's density with water, seawater, ethanol, glycerol, mercury or a density you enter, and says whether it sinks or floats.
- 4. Read the results. You get the working, specific gravity, a close match from the reference table when there is one, and the density in every supported unit.
The Density Formula
Density
ρ = m / V
Mass
m = ρ × V
Volume
V = m / ρ
Density ρ is mass per unit volume. The SI unit is kg/m³, but chemistry mostly uses g/cm³, which is identical to g/mL because one millilitre is exactly one cubic centimetre. Water at 20 °C is 0.9982 g/mL, so its density in kg/m³ is 998.2; the numbers differ by a factor of 1,000 between the two unit systems, which is the most common source of errors. Density depends on temperature, and for gases on pressure, so a density without a temperature is incomplete.
Worked Examples
Density (the default inputs). A metal block has a mass of 54.0 g and a volume of 20.0 cm³. ρ = 54.0 g ÷ 20.0 cm³ = 2.70 g/cm³. That is 2700 kg/m³ or 169 lb/ft³, and it matches aluminum's 2.70 g/mL in the reference table. It also sinks in water, because 2.70 is greater than 0.9982.
Mass from density. What does 250.0 mL of ethanol weigh? At 0.7893 g/mL, m = 0.7893 × 250.0 = 197.3 g.
Volume from mass. What volume is 500.0 g of mercury? With ρ = 13.55 g/mL, V = 500.0 ÷ 13.55 = 36.90 mL — a small volume for a heavy liquid.
Sink or float. Ice has a density of 0.917 g/mL and liquid water 0.9982 g/mL, so ice floats with 0.917 ÷ 0.9982 = 91.9% of its volume below the surface. In seawater (about 1.025 g/mL) the figure is about 89.5%, which is the origin of the saying that most of an iceberg is underwater.
Finding the volume of an irregular object
Lower the object into a graduated cylinder part-filled with water and read the rise in level; the difference is its volume (displacement). This works for any solid that does not float or dissolve. For dimensions you can measure, use geometry: a cube is the side cubed, a cylinder is πr²h. Give the mass and volume the right number of figures with the Significant Figures Calculator.
Specific Gravity and Common Mistakes
Specific gravity, or relative density, is a substance's density divided by that of water, and it has no unit. The calculator divides by water at 4 °C (0.999975 g/mL), so numerically it is almost identical to the density in g/mL.
- Mixing g/mL and kg/m³. 1 g/cm³ is 1000 kg/m³. If an answer is a thousand times too large or small, check the units first.
- Using the wrong temperature. Liquids expand when heated, so their density falls; quote the temperature with a density.
- Assuming density identifies a material. Alloys, porosity and impurities change it, so a match is a hint, not proof.
- Confusing mass with weight. Density uses mass. If your balance reads in newtons or pounds-force, convert first; the Unit Converter can help.
Frequently Asked Questions
- What is the formula for density?
- Density equals mass divided by volume, ρ = m/V. Rearranged, mass is density times volume and volume is mass divided by density. Keep the units consistent: grams with millilitres gives g/mL, and kilograms with cubic metres gives kg/m³.
- What is the density of water?
- Pure water is 0.9982 g/mL (998.2 kg/m³) at 20 °C and reaches its maximum of about 0.99997 g/mL near 4 °C. Because it is so close to 1 g/mL, many quick calculations treat 1 mL of water as 1 g, which is fine for rough work but not for precise measurements.
- How do you know if an object will sink or float?
- Compare densities. An object less dense than the fluid floats, with the fraction of its volume below the surface equal to the ratio of the two densities; an object denser than the fluid sinks. The calculator does this for water, seawater, ethanol, glycerol, mercury or a fluid of your choice.
- How do I convert g/cm³ to kg/m³?
- Multiply by 1,000: 2.70 g/cm³ is 2700 kg/m³. In the other direction, divide by 1,000. The same factor converts g/mL to kg/m³ and kg/L to g/L.
- What is the difference between density and specific gravity?
- Density has units (g/mL, kg/m³); specific gravity is the ratio of a substance's density to water's, so it is dimensionless. In the metric system the two are numerically almost the same in g/mL, which is why specific gravity is quoted for liquids such as urine, battery acid and wine must.
- Why is my measured density different from the table value?
- Reference values are for pure substances at a stated temperature. Real samples contain impurities or voids, and measuring volume by displacement or by ruler carries its own uncertainty. A percent error against the table value shows how large the gap is; use the Percent Error Calculator for that.