Calculator · Fluid Mechanics
Density & Specific Gravity Calculator
Three quantities that describe how heavy a fluid is: density ρ, the dimensionless specific gravity SG against a reference fluid, and the specific weight γ, which is the weight of a unit volume. Nothing else about the fluid is assumed here — this is not a property database.
Inputs
Water at 1000 kg/m³ is the usual reference for liquids. It is stated, never assumed.
Specific weight uses the standard gravitational acceleration g = 9.80665 m/s².
Results
Density ρ
| Density ρ | 1000 kg/m³ |
|---|---|
| Specific gravity SG = ρ/ρ_ref | 1 |
| Specific weight γ = ρg | 9806.65 N/m³ |
Assumptions
- · Uniform sample: the mass fills the stated volume.
Explore in the Lab
The density carries across to the pressure field, the submerged surface and the buoyant force.
Technical reference
ρ = m / V
SG = ρ / ρ_ref
ρ = SG · ρ_ref
γ = ρ g
- ρ
- density[kg/m³]
- m
- mass of the sample[kg]
- V
- volume the sample fills[m³]
- ρ_ref
- reference density, stated by you[kg/m³]
- SG
- specific gravity, a ratio[—]
- γ
- specific weight, weight per unit volume[N/m³]
The sample is treated as uniform: the whole mass fills the whole volume. Mass and volume must both be positive; a fluid of zero density is not a physical state.
Specific gravity is dimensionless and only means something once the reference fluid is named. Water at 1000 kg/m³ is the usual reference for liquids, air for gases — this calculator never picks one for you.
Specific weight is a weight per unit volume, so it depends on gravity. Density does not.
Temperature and pressure change the density of a real fluid. Enter the density at the state you are working at; nothing here interpolates a property table.
Viscosity is a separate property and is not part of this calculator.