Density Units
Density units combine a mass unit with a volume unit. Because volume uses cubed length, density conversions are a little more treacherous than they look at first glance.
Common density units
The SI unit is kg/m³. Common alternatives include g/cm³, g/mL, kg/L, lb/ft³ and lb/in³. Choose a unit appropriate to the field and keep source conditions attached to property values.
Core conversions
| From | To |
|---|---|
| 1 g/cm³ | 1000 kg/m³ |
| 1 g/mL | 1000 kg/m³ |
| 1 kg/L | 1000 kg/m³ |
| 1 kg/m³ | 0.062428 lb/ft³ |
Why cubic unit conversions cause errors
Length conversion factors must be cubed for volume. Since 1 m = 100 cm, 1 m³ = 100³ cm³ = 1,000,000 cm³. Forgetting that cube is a classic source of six-order-of-magnitude mistakes.
Units vs conditions
Converting units does not change the physical state. Converting a gas density from kg/m³ to lb/ft³ is valid only for the same temperature and pressure. Unit conversion cannot rescue an unstated state condition.
Frequently asked questions
What is the SI unit of density?
kg/m³.
Is g/mL the same as g/cm³?
Yes numerically.
Why is 1 g/cm³ equal to 1000 kg/m³?
Because converting grams to kilograms and cubic centimetres to cubic metres changes both numerator and denominator.
Sources & references
We prefer standards bodies, government/scientific agencies and primary technical references. Reference values can vary with conditions, grade, composition or measurement method.
Related calculators & guides
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