Free Density Converter
Convert density units instantly — kg/m³, g/cm³, g/mL, lb/ft³, lb/in³, slug/ft³, and more. Free, symmetrical, no sign-up.
Exact Conversion Formula & Multipliers
Density conversions scale directly with the mass and volume units they're built from: 1 g/cm³ = 1,000 kg/m³ exactly, and 1 lb/ft³ = 16.01846337396 kg/m³. Pure water at 4°C has a density of almost exactly 1,000 kg/m³ (1 g/cm³) — the reference point around which the metric system's mass unit was originally calibrated, which is why water density conversions come out to such clean numbers.
Practical Real-World Scenarios
- Materials science and manufacturing: material datasheets specify density in g/cm³ or kg/m³ internationally, requiring conversion when working with US lb/ft³ specifications.
- Fluid dynamics and shipping: cargo and fuel density affects buoyancy and load calculations, critical in maritime shipping where different countries' documentation uses different unit systems.
- Cooking and food science: ingredient density (grams per milliliter) underlies why volume-to-weight conversions differ between flour, sugar, and liquid ingredients in recipes.
Historical & Technical Background
Density as a concept dates back to Archimedes' famous (if possibly apocryphal) crown problem in ancient Greece, where he reportedly used water displacement to detect a fraudulent gold crown by comparing density to pure gold. The deliberate calibration of the original metric gram to the mass of one cubic centimeter of water at its most dense temperature (4°C) is why metric density figures for water-like substances tend to be clean, round numbers, while imperial density figures rarely are.
Precision & Accuracy Statement
Conversion factors use the exact defined values given in NIST Special Publication 811 and the BIPM SI Brochure wherever such a definition exists (for example 1 lb = 0.45359237 kg, 1 in = 2.54 cm, 1 US gal = 3.785411784 L, g₀ = 9.80665 m/s²); derived factors are computed from those definitions rather than copied as rounded figures. Results are calculated in double-precision floating point and shown to 10 significant digits, so the last digit can differ by one unit of rounding. The rounded figures in the text and tables above are for reading convenience.
How This Converter Works
Density is critical in materials science, chemistry, and engineering. SI uses kg/m³, chemistry uses g/cm³ or g/mL, and US engineering uses lb/ft³. Our converter handles 11 density units simultaneously.
Common Conversions
| Material | kg/m³ | g/cm³ | lb/ft³ |
|---|---|---|---|
| Air (at 20°C) | 1.204 kg/m³ | 0.001204 g/cm³ | 0.0752 lb/ft³ |
| Water (at 4°C) | 1,000 kg/m³ | 1.0 g/cm³ | 62.43 lb/ft³ |
| Concrete | 2,400 kg/m³ | 2.4 g/cm³ | 149.8 lb/ft³ |
| Aluminium | 2,700 kg/m³ | 2.7 g/cm³ | 168.6 lb/ft³ |
| Steel | 7,850 kg/m³ | 7.85 g/cm³ | 490 lb/ft³ |
| Gold | 19,300 kg/m³ | 19.3 g/cm³ | 1,205 lb/ft³ |