Density Unit Converter
Convert density between kg/m³, g/cm³, lb/ft³, lb/in³, and oz/in³.
What it does
Density is mass per unit volume. A scientist may write grams per cubic centimeter, an engineer may use kilograms per cubic meter, and a fabricator may work in pounds per cubic foot. The number can describe the same material while looking very different.
This converter moves between five common density units. It first converts the input to kilograms per cubic meter, then divides by the target factor. Specific gravity is shown at the same time because it is often the number used to compare materials.
The default is 7.85 grams per cubic centimeter, a common value for carbon steel. That equals 7,850 kilograms per cubic meter, 490.05949 pounds per cubic foot, and a specific gravity of 7.8500 against water at 4 °C. A steel part is about 7.85 times as dense as the same volume of water.
Specific gravity has no units. It is the density of a material divided by the density of water, usually taken as 1,000 kilograms per cubic meter at 4 °C. A value below 1 means the material can float in water, while a value above 1 means it will sink unless trapped air changes the average density.
Real materials vary. Alloy composition, heat treatment, moisture, and porosity can move density by several percent. Use the converter for estimates and material comparisons, not as a substitute for a measured value when a small difference matters.
How to use
- Enter the density value you already have.
- Pick the unit that matches that value.
- Pick the unit you want in the answer.
- Press Calculate to update the result.
- Read the converted density and specific gravity.
- Use the all-units note to compare the same density in every unit.
Formula
- density_source
- Density in the selected source unit.
- factor
- 1 for kg/m³, 1,000 for g/cm³, 16.0184633739601 for lb/ft³, 27,679.9047102031 for lb/in³, and 1,729.99404439163 for oz/in³.
- SG
- Specific gravity, a unitless ratio against water at 4 °C.
The factors convert each unit to kilograms per cubic meter. For 7.85 g/cm³, multiply by 1,000 to get 7,850 kg/m³. Divide by 16.0184633739601 to get 490.05949 lb/ft³. Specific gravity is 7,850 / 1,000 = 7.8500. The tool shows eight significant digits for the converted density and four decimal places for specific gravity.
Worked example
Example: steel at 7.85 g/cm³
Defaults: 7.85 g/cm³ converted to kg/m³.
- Source factor: 1 g/cm³ = 1,000 kg/m³.
- Convert: 7.85 x 1,000 = 7,850 kg/m³.
- Specific gravity: 7,850 / 1,000 = 7.8500.
- Pounds per cubic foot: 7,850 / 16.0184633739601 = 490.05949 lb/ft³.
- Pounds per cubic inch: 7,850 / 27,679.9047102031 = 0.28359924 lb/in³.
- Tool shows 7,850 kg/m³ and 7.8500 specific gravity.
Reference table
| Material | kg/m³ | g/cm³ | lb/ft³ | Specific gravity |
|---|---|---|---|---|
| Water at 4 °C | 1,000 | 1.000 | 62.427961 | 1.0000 |
| Aluminum | 2,700 | 2.70 | 168.55549 | 2.7000 |
| Steel | 7,850 | 7.85 | 490.05949 | 7.8500 |
| Lead | 11,340 | 11.34 | 707.93307 | 11.3400 |
| Air at sea level | 1.225 | 0.001225 | 0.076474252 | 0.0012 |
Limits
- Specific gravity uses 1,000 kg/m³ for water; water density changes with temperature.
- Alloy, moisture, and porosity make real material densities differ from table values.
- The converter treats density as one number, not a measured range.
- It does not measure density; it only converts a value you provide.
Common mistakes
- Using 1,000 lb/ft³ for water instead of about 62.428 lb/ft³.
- Reporting specific gravity with units when it is a ratio.
- Dividing by 1,000 when moving from g/cm³ to kg/m³ instead of multiplying.
- Mixing pounds per cubic inch with pounds per cubic foot.
- Assuming a single density fits every alloy of a metal.
Try it yourself
Quick checks. Answers sit tucked under each question.
Convert 1 g/cm³ to kg/m³ and give specific gravity.
1,000 kg/m³ and 1.0000 specific gravity.
Convert 62.4 lb/ft³ to kg/m³ and give specific gravity.
999.55211 kg/m³ and 0.9996 specific gravity.
Convert 0.0361273 lb/in³ to g/cm³.
1.0000002 g/cm³ and 1.0000 specific gravity.
Questions
How many kg/m³ are in 1 g/cm³?
There are 1,000 kg/m³ in 1 g/cm³ because a cubic meter holds one million cubic centimeters and a kilogram is 1,000 grams.
How do you calculate specific gravity?
Divide the material density in kg/m³ by 1,000. Steel at 7,850 kg/m³ has a specific gravity of 7.8500.
Is specific gravity unitless?
Yes. It is a ratio of two densities, so the units cancel.
How many lb/ft³ are in 1 g/cm³?
About 62.427961 lb/ft³. One kilogram per cubic meter is about 0.062427961 lb/ft³.
Why is steel shown as 7.85 g/cm³?
That is a common value for carbon steel. Stainless steel, cast iron, and alloy steels can differ.
Does temperature matter?
Yes. Water reaches about 1,000 kg/m³ near 4 °C, and most materials expand when heated, which lowers density.
Sources
- NIST SP 811 Appendix B.9: density conversion factors
- NIST SP 811 Appendix B.8: conversion factors
- BIPM: SI Brochure