Density Converter

Convert between density units (mass per volume) including g/cm³, kg/m³, lb/ft³, and more.

Common Material Densities

Common Density Conversions

Water Treatment Conversions

• 1 g/L = 1000 mg/L (ppm for water)
• 1 mg/L ≈ 0.0000835 lb/gal (US)
• 1 lb/gal (US) ≈ 119826 mg/L
• 1 gr/gal (US) ≈ 17.118 mg/L

Material Density Examples

Gases at STP (kg/m³)

• Hydrogen: 0.0899
• Helium: 0.179
• Nitrogen: 1.251
• Air: 1.293
• Oxygen: 1.429
• Carbon Dioxide: 1.977

About Density

Density is the measure of mass per unit volume. It determines how much "stuff" is packed into a given space and is fundamental in chemistry, physics, engineering, and many industries.

Definition and Formula

ρ = m / V

Where:

• ρ (rho) = density
• m = mass
• V = volume

Standard Units

SI Unit: kg/m³ (kilogram per cubic meter)

CGS Unit: g/cm³ (gram per cubic centimeter)

Common: g/mL and g/cm³ are numerically equal and most convenient for liquids and solids.

Note: 1 g/cm³ = 1 g/mL = 1 kg/L = 1000 kg/m³ = 62.428 lb/ft³

Specific Gravity

Specific gravity (SG) is the ratio of a substance's density to the density of water at 4°C (1 g/cm³). It's dimensionless and convenient for comparing densities:

SG = ρ_substance / ρ_water

• SG = 1.0: Same density as water (floats neutrally)
• SG < 1.0: Less dense than water (floats)
• SG > 1.0: Denser than water (sinks)

For liquids and solids, numerically: SG ≈ density in g/cm³

Temperature Dependence

Density varies with temperature because volume changes with temperature while mass stays constant:

• Liquids & Gases: Density decreases as temperature increases (thermal expansion)
• Water anomaly: Water is densest at 4°C (3.98°C exactly), not at 0°C
• Ice floats: Ice (0.917 g/cm³) is less dense than liquid water
• Standard conditions: Densities usually reported at 20°C or 25°C

Pressure Dependence

• Solids & Liquids: Nearly incompressible, density barely changes with pressure
• Gases: Highly compressible, density proportional to pressure (Ideal Gas Law)
• STP: Standard Temperature and Pressure (0°C, 1 atm) used for gas density reference

Water Treatment & ppm

In water treatment and environmental chemistry, concentrations are often expressed in mg/L:

• 1 mg/L ≈ 1 ppm (parts per million) for dilute aqueous solutions
• This approximation assumes water density = 1 g/mL
• Used for measuring pollutants, minerals, chlorine, etc.
• Example: Drinking water chlorine: 0.2-2.0 mg/L

Why Density Matters

• Material identification: Each substance has characteristic density
• Purity testing: Density changes with impurities
• Buoyancy: Determines if objects float or sink
• Separation: Centrifuges separate by density differences
• Quality control: Beverages, fuels, chemicals tested by density
• Engineering: Structural calculations need material density
• Medicine: Bone density, urine specific gravity diagnostics

Density Ranges

• Gases: ~0.001 g/cm³ (very low)
• Liquids: 0.7-1.6 g/cm³ (most common)
• Solids: 0.5-20 g/cm³ (wide range)
• Densest element: Osmium at 22.59 g/cm³
• Lightest solid: Aerogel at ~0.001 g/cm³

Circular Mil Foot

The pound per circular mil foot (lb/cmil·ft) is a specialized unit for electrical conductor density:

• Used primarily for wire and cable specifications
• 1 circular mil = area of circle with 1 mil (0.001") diameter
• Convenient for comparing conductor materials
• Copper: 0.00328 lb/cmil·ft
• Aluminum: 0.00101 lb/cmil·ft

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