This calculator computes the density, specific weight and specific gravity of a material or fluid. Density is defined as mass per unit volume of a substance, specific weight measures the weight (force) per unit volume exerted by gravity, and specific gravity compares the density of a substance (i.e., water). These concepts are fundamental for understanding the behavior and characteristics of materials and fluids across various engineering disciplines.
Density
Calculation
Inputs
m
:1.00kg
V
:2.00m3
Output
ρ
:0.50kg/m3
ρ=Vm
Where:
ρ
= Density
[m3kg]
m
= Mass
[kg]
V = Volume
[m3
]
Imperial (U.S.) unit convention
Explanation
Particles within a material with a higher density are packed closer together at the atomic level. Density is a physical characteristic that remains constant at a specific temperature and pressure. It can be useful for the identification of substances.
Density and state of matter from low density to high density
Specific Weight
Calculation
Inputs
ρ (1)
:0.50kg/m3
ag
:9.81m/s2
Output
γ
:4.91N/m3
γ=ρ×ag
Where:
ρ
= Density
[m3kg]
ag
= acceleration of gravity =
9.81m/s2
γ
= Specific Weight
[N/m3]
or
[kN/m3]
Explanation
Unlike density, specific weight is not a fixed property of a material as it depends on the value of the gravitational acceleration. Depending on the material's bulk modulus (i.e. material resistance to compression), pressure may also affect values, however at moderate pressures, it usually has less of an impact than the other variables. Pressure can influence specific weight, but its impact is typically less significant compared to other factors such as temperature. the degree to which pressure affects specific weight depends on the material's bulk modulus. Generally, at moderate pressure, the pressure effect is minor. However, materials with low bulk modulus may experience differently.
Table of Specific Weight for Some Common Materials
Specific Gravity
Calculation
For Relative Density:
Inputs
ρs
:1.00kg/m3
ρw
:1.00kg/m3
Output
SG
:1.00
SGρ=ρwρs
For Gases:
Inputs
ρg
:2.00kg/m3
ρa
:2.00kg/m3
Output
SG (1)
:1.00
SGg=ρaρg
Where:
ρs
= density of substance
[m3kg]
ρw
= density of water at
4oC
[m3kg]
ρg
= density of gas
[m3kg]
ρa
= density of air at Normal Temperature and Pressure (NTP)
[m3kg]
, which is at
20oC
and 1 atm, respectively
SGg
= Specific Gravity (dimensionless)
Explanation
Specific gravity (relative density) is a dimensionless unit defined as the ratio of the density of a substance to the density of water at a specified temperature. It is commonly used the density of water at
4oC
since water at this point has its highest density of
1000kg/m3
.
Similarly, the specific gravity of gases is defined as the ratio of the density of gases to the density of the air at the specified temperature and pressure.
Table of Specific Gravity for Some Common Materials