Density Units Converter
Convert density values between kg/m³, g/cm³, g/mL, lb/ft³, lb/in³ and more. Enter a value, pick a unit, and get the equivalent density in all common units at once.
Convert Density Units
Density Converter Formula
Where:
- \(\rho_{\text{input}}\) — the density value you entered
- \(f_{\text{input}}\) — factor that converts the input unit to kg/m³ (see table below)
- \(f_{\text{target}}\) — factor that converts the target unit to kg/m³
- \(\rho_{\text{target}}\) — the same density expressed in the target unit
Every unit is first converted to kilograms per cubic meter (the SI base unit for density), then divided by the target unit's factor. This two-step method guarantees consistent results for any pair of units.
Density Converter – Calculation Example
Example: convert 1 g/cm³ — the density of water at 4 °C — into all other units.
\[
\rho = 1 \ \text{g/cm}^3 \times 1000 = 1000 \ \text{kg/m}^3
\]
\[
1000 \div 1000 = 1 \ \text{g/mL}, \quad 1000 \div 16.018463 = 62.427961 \ \text{lb/ft}^3, \quad 1000 \div 27679.905 = 0.036127 \ \text{lb/in}^3
\]
Result: 1 g/cm³ = 1000 kg/m³ = 1 kg/L = 1 g/mL = 1000 g/L = 62.427961 lb/ft³ = 0.036127 lb/in³ = 0.578037 oz/in³ = 8.345404 lb/gal (US).
How to Use the Density Converter
- Type your value into the Density value field (it must be zero or positive).
- Choose the unit of that value from the Unit dropdown: kg/m³, g/cm³, g/mL, lb/ft³ or lb/in³.
- Read the results table: it shows your density converted into every other common unit — kg/m³, g/cm³, g/mL, g/L, kg/L, lb/ft³, lb/in³, oz/in³ and lb/gal (US).
What Is Density?
Density is the amount of mass packed into a given volume, defined as \( \rho = m / V \). It tells you how heavy a fixed amount of a substance is: a cubic centimeter of lead (about 11.34 g/cm³) weighs far more than a cubic centimeter of water (1 g/cm³). Density is a key property in physics, chemistry, engineering, geology and quality control, because it identifies substances, predicts whether objects float or sink, and links mass to volume in design calculations.
Density values appear in many unit systems, which is why conversion matters. Scientific work uses SI units (kg/m³), laboratories and medicine often report g/mL or g/L, while US engineering frequently uses lb/ft³, lb/in³ or lb/gal. The metric units are related exactly: 1 g/cm³ = 1 g/mL = 1 kg/L = 1000 kg/m³, since 1 mL = 1 cm³ and 1 L = 0.001 m³. Imperial units are less round: 1 lb/ft³ ≈ 16.018463 kg/m³ and 1 lb/in³ ≈ 27679.905 kg/m³, so a quick mental conversion is rarely accurate enough.
When interpreting results, remember that density depends on temperature and pressure. Gases expand when heated, lowering their density, and even liquids and solids change slightly. Water reaches its maximum density of about 999.97 kg/m³ at 4 °C, which is the value behind the familiar "1 g/cm³" figure. If your source data was measured at a different temperature, expect small deviations.
Conversion Factors and Reference Values
The table below lists the factors the calculator uses internally. To convert a value from one unit to another, multiply by the source factor and divide by the target factor.
| Unit | Factor to kg/m³ |
|---|---|
| kg/m³ | 1 |
| g/cm³ | 1000 (exact) |
| g/mL | 1000 (exact) |
| g/L | 1 (exact) |
| kg/L | 1000 (exact) |
| lb/ft³ | 16.018463 |
| lb/in³ | 27679.905 |
| oz/in³ | 1729.994 |
| lb/gal (US) | 119.826427 |
Some densities worth remembering: air at sea level ≈ 1.225 kg/m³, water ≈ 1000 kg/m³, steel ≈ 7850 kg/m³, gold ≈ 19.32 g/cm³.
Notes and Limitations
- The calculator converts units only — it does not compute density from mass and volume. For that, divide mass by volume first, or use a dedicated mass/volume calculation.
- Results are rounded to 6 decimal places. For most engineering and scientific purposes this is more than sufficient; for extreme values (very large or very small), scientific notation may be more convenient.
- The pound- and gallon-based units use US definitions (1 lb = 0.45359237 kg, 1 US gallon = 3.785411784 L). Imperial (UK) gallons are not included.
- Density is assumed constant, i.e. the calculator does not adjust for temperature or pressure. Values measured under different conditions may differ slightly.
- The source unit you select is omitted from the results table to avoid a redundant row.
If you also work with related physical quantities, you may find our Mass Flux Density Converter, Pressure Converter or Speed Converter useful for keeping every part of a calculation in consistent units.
Frequently Asked Questions
How do I convert density by hand without a calculator?
Convert to kg/m³ first, then to the target unit. For example, 50 lb/ft³ to g/cm³: multiply 50 by 16.018463 to get 800.923 kg/m³, then divide by 1000, giving 0.800923 g/cm³. Handy mental anchors: 1 g/cm³ = 1000 kg/m³ exactly, and 1 lb/ft³ ≈ 16.02 kg/m³. For quick estimates, dividing lb/ft³ by 62.4 gives you g/cm³, since water is about 62.4 lb/ft³.
Are g/cm³, g/mL and kg/L really the same unit?
Yes, they are exactly equal. Because 1 mL = 1 cm³ by definition and 1 L = 1000 cm³, a density of 1 g/cm³ = 1 g/mL = 1 kg/L = 1000 kg/m³. Laboratories often use g/mL, chemistry textbooks use g/cm³, and industry uses kg/L, but they are interchangeable — no conversion needed, just move the decimal point when switching to kg/m³.
What is the difference between US and imperial (UK) gallons in density?
They differ by about 20%. A US gallon is 3.785 L, while an imperial gallon is 4.546 L. So 1 lb/gal (US) ≈ 119.83 kg/m³, but 1 lb/gal (UK) ≈ 99.78 kg/m³. This calculator uses US definitions. If your data comes from a UK source labeled lb/gal, verify which gallon is meant — using the wrong one introduces an error of roughly 17%.
How is specific gravity related to density units?
Specific gravity is the ratio of a substance's density to the density of water (about 1000 kg/m³ or 62.4 lb/ft³). It is dimensionless. To convert specific gravity to density, multiply by water's density in your desired unit: a specific gravity of 2.7 means 2700 kg/m³, 2.7 g/cm³, or about 168.6 lb/ft³. Since water's density varies slightly with temperature, precise work should state the reference temperature.
Why does my converted value not match a reference table exactly?
The most common reason is temperature. Density changes with temperature because materials expand and contract, so a value measured at 20 °C will not match one measured at 4 °C. Gases are especially sensitive — air density drops noticeably with just a few degrees of warming. Rounding in published tables and different standards (US vs UK gallons, international vs avoirdupois ounce) also cause small discrepancies.
Is lb/ft³ a density of mass or weight?
In this converter, lb/ft³ (pounds per cubic foot) is treated as mass density, using the international avoirdupois pound defined as exactly 0.45359237 kg. Some US engineering texts report