Density Converter — kg/m³, g/cm³, lb/ft³, Specific Gravity & More

The Formula

Density conversion uses linear factors relative to the base SI unit (kg/m³). Density is mass per unit volume. Specific gravity (SG) is a dimensionless ratio of a substance's density to the density of water at 4°C (1,000 kg/m³), so SG 1 = 1,000 kg/m³ = 1 g/cm³. For example, converting 1 lb/ft³ to kg/m³: 1 × 16.0185 ÷ 1 = 16.02 kg/m³.

Variable Definitions

How to Use This Calculator

1. 1

   Enter the density value you want to convert in the "Value" field.

2. 2

   Select the current density unit from the "From" dropdown.

3. 3

   Select the desired density unit from the "To" dropdown.

4. 4

   The converted value is displayed instantly. Use specific gravity (SG) to compare material density to water.

5. 5

   Use the quick reference table for density values of common materials like water, air, aluminum, and gold.

Quick Reference

Common Applications

• Battery acid (lead-acid): SG 1.28 when fully charged
• Engine coolant: SG 1.06–1.12 (antifreeze mixture)
• Seawater: ~1,025 kg/m³ / SG 1.025
• Aluminum vs steel: 2,700 vs 7,800 kg/m³ (steel is ~3× denser)
• Urine specific gravity: 1.005–1.030 (clinical diagnostic range)
• API gravity (petroleum): API 30° ≈ SG 0.876 (light crude)

Density determines if an object floats (SG < 1) or sinks (SG > 1) in water

Understanding the Concept

Density is a fundamental material property — how much mass occupies a given volume. It determines whether objects float or sink, affects structural weight calculations, and is essential for fluid dynamics, material selection, and quality control in manufacturing. Water at 4°C (its maximum density) has a density of exactly 1 g/cm³, 1,000 kg/m³, or SG 1.0. This is the reference point for specific gravity — gold is 19.3 times denser than water (SG 19.3), meaning a gold bar the size of a water bottle weighs as much as 19 water bottles. Air has a density of about 1.225 kg/m³ at sea level (1/815th the density of water). This large difference explains why sound travels faster in water than in air. Density varies with temperature and pressure — hot air rises because it is less dense, and cold water sinks because it is denser. Material density determines practical applications: aluminum (2.7 g/cm³) is used in aircraft because it is light, tungsten (19.3 g/cm³) in radiation shielding because it is dense.

Frequently Asked Questions

Sources & References