Density Converter — kg/m³, g/cm³, lb/ft³ & More
Convert between 16 density units simultaneously — type in any field and all others update instantly. Covers all SI metric units, imperial units, specific gravity, and more. Includes a materials reference panel with densities of common substances. Free, no account.
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How to convert density units
The most complete free online density converter
Density Unit Conversion — kg/m³, g/cm³, lb/ft³ Complete Guide
Density measures the mass of a substance per unit volume. The SI unit is kilograms per cubic metre (kg/m³). In chemistry and materials science, grams per cubic centimetre (g/cm³) is common — conveniently equal to g/mL for liquids. In US engineering, pounds per cubic foot (lb/ft³) and pounds per cubic inch (lb/in³) are standard. All of these units measure the same physical quantity from different perspectives.
Conversion formulas
Density of common materials
| Material | kg/m³ | g/cm³ | lb/ft³ | Specific gravity |
|---|---|---|---|---|
| Air (sea level, 15°C) | 1.225 | 0.001225 | 0.0765 | 0.00123 |
| Aerogel | 1 – 160 | 0.001 – 0.16 | 0.062 – 10 | 0.001 – 0.16 |
| Wood (pine) | 400 – 600 | 0.40 – 0.60 | 25 – 37 | 0.40 – 0.60 |
| Water (4°C) | 1000 | 1.000 | 62.43 | 1.000 |
| Seawater | 1025 | 1.025 | 64.0 | 1.025 |
| Concrete | 2000 – 2500 | 2.0 – 2.5 | 125 – 156 | 2.0 – 2.5 |
| Aluminium | 2700 | 2.700 | 168.6 | 2.700 |
| Steel | 7850 | 7.850 | 490 | 7.850 |
| Iron | 7874 | 7.874 | 491 | 7.874 |
| Copper | 8960 | 8.960 | 559 | 8.960 |
| Lead | 11340 | 11.34 | 708 | 11.34 |
| Mercury | 13546 | 13.55 | 846 | 13.55 |
| Gold | 19300 | 19.30 | 1205 | 19.30 |
| Osmium (densest element) | 22590 | 22.59 | 1410 | 22.59 |
What is specific gravity?
Specific gravity (SG) is the ratio of a material's density to the density of water (1000 kg/m³ at 4°C). It is dimensionless. SG = 1 means the same density as water. SG < 1 means the material floats in water (wood, cork, most plastics, ice at SG 0.917). SG > 1 means the material sinks (metals, stone, most liquids denser than water). Converting between SG and kg/m³ is straightforward: multiply SG by 1000 to get kg/m³, or divide kg/m³ by 1000 to get SG.
Why g/cm³ and g/mL are equal
By definition, 1 millilitre (mL) equals exactly 1 cubic centimetre (cm³). This makes g/mL and g/cm³ completely interchangeable units — they measure the same thing and have the same numerical value. Water at 4°C has a density of exactly 1 g/cm³ = 1 g/mL = 1 kg/L = 1000 kg/m³. This convenient equivalence makes density conversions between SI metric units straightforward for liquids in chemistry and pharmacy.
US gallon vs UK gallon in density calculations
The US gallon (3.78541 litres) and the imperial UK gallon (4.54609 litres) differ significantly — the UK gallon is about 20% larger. This means lb/US gal and lb/UK gal give different numbers for the same liquid. Water: 8.345 lb/US gal vs 10.02 lb/UK gal. This difference matters in petroleum, chemical processing, and agricultural applications where gallon-based density specifications are common. The converter above handles both separately to avoid this confusion.
What is slug/ft³ used for?
The slug is a unit of mass in the US customary system defined so that 1 slug accelerates at 1 ft/s² under 1 pound-force. 1 slug = 14.5939 kg. Slug/ft³ is used in aerodynamics, fluid mechanics, and structural engineering calculations in the US. Air at sea level has a density of approximately 0.002377 slug/ft³, which is the value used in many aerodynamics equations. Converting slug/ft³ to kg/m³ requires multiplying by 515.379.
Density converter FAQ
Divide by 1000. 1000 kg/m3 = 1 g/cm3. 7874 kg/m3 (iron) = 7.874 g/cm3. To convert back, multiply by 1000. This is the most common density conversion in science and engineering.
Multiply by 1000. 1 g/cm3 (water) = 1000 kg/m3. 2.7 g/cm3 (aluminium) = 2700 kg/m3. 19.3 g/cm3 (gold) = 19300 kg/m3.
Multiply by 16.01846. 62.43 lb/ft3 (water) = 1000 kg/m3. 490 lb/ft3 (steel) = 7849 kg/m3. To convert kg/m3 to lb/ft3, divide by 16.01846.
Specific gravity (SG) is the ratio of a material's density to water's density (1000 kg/m3). SG = kg/m3 / 1000. Water SG = 1.0. Aluminium SG = 2.7. Lead SG = 11.34. SG below 1 floats in water; above 1 sinks.
Water at 4C: 1000 kg/m3, 1 g/cm3, 1 g/mL, 1 kg/L, 62.43 lb/ft3, 0.03613 lb/in3, 8.345 lb/US gal, 10.02 lb/UK gal, 1.940 slug/ft3, specific gravity 1.0.
Multiply by 1000. g/mL and g/cm3 are identical units (1 mL = 1 cm3). 1 g/mL = 1000 kg/m3. 0.789 g/mL (ethanol) = 789 kg/m3. 13.6 g/mL (mercury) = 13600 kg/m3.
Used in US aerodynamics and fluid mechanics. 1 slug/ft3 = 515.379 kg/m3. Air at sea level = 0.002377 slug/ft3. The slug is a mass unit where 1 slug x 1 ft/s2 = 1 pound-force.
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