# Density converter

> Convert g/cm³ to kg/m³, kg/m³ to lb/ft³ and lb/gal (ppg), and g/mL to kg/L, with exact factors from the 1959 pound and foot.

Interactive version: https://www.calcopenly.com/conversion/density-converter
Subject: Unit converters

Density is mass per volume, so each unit is a mass unit divided by a volume unit, held here as kilograms per cubic metre. The metric units differ by powers of 1,000 (1 g/cm³ = 1 g/mL = 1 kg/L = 1,000 kg/m³), and the imperial ones follow from the exact pound and foot: 1 lb/ft³ = 16.0185 kg/m³.

The default converts 1 g/cm³, close to the density of water, to 62.428 lb/ft³. Engineers use lb/ft³ (pcf) for soils and concrete, drillers use lb/gal (ppg) for drilling mud, and materials data sheets use g/cm³.

Density changes with temperature, and the converter only changes units. Pure water is densest near 4 °C at 999.97 kg/m³ and is 998.2 kg/m³ at 20 °C, so “1 g/cm³ for water” is right to within 0.2%.

## Inputs

- **Value**: A number in the “from” unit, or with its own unit
- **From** (options: kilogram per cubic metre (kg/m³), gram per cubic centimetre (g/cm³), gram per millilitre (g/mL), kilogram per litre (kg/L), pound per cubic foot (lb/ft³), pound per cubic inch (lb/in³), pound per US gallon (lb/gal))
- **To** (options: kilogram per cubic metre (kg/m³), gram per cubic centimetre (g/cm³), gram per millilitre (g/mL), kilogram per litre (kg/L), pound per cubic foot (lb/ft³), pound per cubic inch (lb/in³), pound per US gallon (lb/gal))

## Results

- Converted value — main result
- Conversion
- Conversion factor
- Exactness

## Formula

$$
\begin{gathered} x_{\text{to}} = x_{\text{from}} \times \dfrac{f_{\text{from}}}{f_{\text{to}}} \\ f = \text{one unit expressed in } \text{kg/m³} \end{gathered}
$$

## Worked examples

### 1 g/cm³ in lb/ft³

- Value: 1 g/cm³
- From: gram per cubic centimetre (g/cm³)
- To: pound per cubic foot (lb/ft³)
- **Converted value: 62.4279605761 lb/ft³**
- Checked against: 1000 kg/m³ ÷ (0.45359237 kg / 0.028316846592 m³) = 14158423296/226796185 (Python 3.8 fractions from the legal definitions)

### 1000 kg/m³ in g/mL

- Value: 1000 kg/m³
- From: kilogram per cubic metre (kg/m³)
- To: gram per millilitre (g/mL)
- **Converted value: 1 g/mL**
- Checked against: 1000 kg/m³ = 1 g/cm³ = 1 g/mL

### 1 lb/gal in kg/m³

- Value: 1 lb/gal
- From: pound per US gallon (lb/gal)
- To: kilogram per cubic metre (kg/m³)
- **Converted value: 119.826427317 kg/m³**
- Checked against: 0.45359237 / 0.003785411784 (Python 3.8 fractions from the legal definitions)

### 1 lb/in³ in g/cm³

- Value: 1 lb/in³
- From: pound per cubic inch (lb/in³)
- To: gram per cubic centimetre (g/cm³)
- **Converted value: 27.6799047102 g/cm³**
- Checked against: 0.45359237 kg / 0.000016387064 m³ ÷ 1000 (Python 3.8 fractions from the legal definitions)

## Questions

### How do I convert g/cm³ to kg/m³?

Multiply by 1,000. A cubic metre holds 10⁶ cubic centimetres and a kilogram is 1,000 grams, so 1 g/cm³ = 1,000 kg/m³. Aluminium at 2.70 g/cm³ is 2,700 kg/m³, and steel at about 7.85 g/cm³ is 7,850 kg/m³. g/mL and kg/L are the same size as g/cm³.

### What is specific gravity?

The ratio of a substance's density to the density of water, so it has no unit. Referenced to water at 4 °C (999.97 kg/m³), specific gravity equals the density in g/cm³ to within 0.003%: a liquid of 0.80 g/cm³ has a specific gravity of 0.80. Other references, such as water at 60 °F, change the fourth significant digit.

### How do I convert lb/ft³ to kg/m³?

Multiply by 16.0185. A pound is 0.45359237 kg and a cubic foot 0.028316846592 m³, both exact, so 1 lb/ft³ = 16.01846337 kg/m³. Normal-weight concrete at about 150 lb/ft³ is about 2,400 kg/m³, and 1,000 kg/m³ is 62.43 lb/ft³.

### What does ppg mean for drilling mud?

Pounds per US gallon, the density unit of oilfield drilling fluids. 1 lb/gal is 119.826 kg/m³, so fresh water at 20 °C is 8.33 ppg and a 12 ppg mud is 1,438 kg/m³, or 1.44 g/cm³. Mud weight sets the pressure the fluid column exerts at the bottom of the well.

### Is the density of water exactly 1 g/cm³?

No, but close. Pure water peaks at 999.97 kg/m³ near 4 °C and is 998.2 kg/m³ at 20 °C. The gram was first defined in 1795 as the mass of 1 cm³ of water, and from 1901 to 1964 the litre was defined as the volume of 1 kg of water, which is why the numbers nearly coincide.

### How accurate is the density converter?

Accuracy depends on your inputs and the method's assumptions. Decimal arithmetic uses 50 significant digits, but estimates, numerical methods and source data can be less precise; the displayed rounding does not remove those limits. It is checked against 4 worked examples whose answers come from independent sources; for example, “1 g/cm³ in lb/ft³” is checked against 1000 kg/m³ ÷ (0.45359237 kg / 0.028316846592 m³) = 14158423296/226796185 (Python 3.8 fractions from the legal definitions).

### Where does the method come from?

NIST SP 811 (2008), Guide for the Use of the SI, Appendix B — conversion factors; NIST Handbook 44, Appendix C — General tables of units of measurement.

## Sources

- [NIST SP 811 (2008), Guide for the Use of the SI, Appendix B — conversion factors](https://www.nist.gov/pml/special-publication-811)
- [NIST Handbook 44, Appendix C — General tables of units of measurement](https://www.nist.gov/pml/owm/nist-handbook-44-current-edition)