# Specific weight

The ratio between weight and volume is called specific weight. The symbol used for specific weight is γ and the SI unit of measurement is N/m3.

$\gamma = \frac{G}{V}=\frac{m \cdot g}{V} \tag{1}$

where:
G [N] – weight
V [m3] – volume
m [kg] – mass
g [m/s2] – gravitational acceleration

The density ρ [kg/m3] is the ratio between mass (m) and volume (V):

$\rho = \frac{m}{V} \tag{2}$

Replacing the expression of the density in formula (1), we get:

$\gamma = \rho \cdot g$

Specific weight, unlike density, is not absolute, it depends on the value of the gravitational acceleration (g), which varies depending on altitude and latitude.

### Example of specific weight (liquid): water

 Temperature [°C] Specific weight [kN/m3] 0 9.805 5 9.807 10 9.804 15 9.798 20 9.789 25 9.777 30 9.765 40 9.731 50 9.690 60 9.642 70 9.589 80 9.530 90 9.467 100 9.399

Image: Specific weight of water

### Example of specific weight (gas): air

 Temperature [°C] Specific weight [N/m3] -40 14.86 -20 13.86 0 12.68 10 12.24 20 11.82 30 11.43 40 11.06 60 10.4 80 9.81 100 9.28 200 7.33

Image: Specific weight of air

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