Specific gravities

What is specific gravity?

Specific gravity (SG) is the ratio of the density of a liquid to the density of water at a defined reference temperature. Water is assigned a specific gravity of 1.0, so fluids heavier than water have an SG above 1.0, while fluids lighter than water have an SG below 1.0.

• SG = 1.0 means the fluid has the same density as water
• SG > 1.0 means the fluid is heavier than water
• SG < 1.0 means the fluid is lighter than water

This makes specific gravity to water a useful reference point when comparing different liquids in pumping, dosing and transfer applications.

Specific gravity formula

The standard formula for specific gravity is:

Specific Gravity = Fluid Density / Water Density

Because it is a ratio, specific gravity has no units.

Specific gravity to water is a simple way of comparing the density of a liquid to the density of water. In pump engineering, specific gravity is an important value because it helps determine how a fluid will affect pump performance, power requirements, sizing and system design. This guide explains what specific gravity means, how it relates to water, and why it matters when selecting pumps for industrial and process applications.

Why specific gravity matters in pump selection

Specific gravity is highly relevant in pump engineering because it affects the power required to move a liquid. A pump handling a heavier liquid may need more power than the same pump handling water, even if the flow rate and head remain the same.

Understanding specific gravity helps with:

• Pump sizing
• Motor sizing
• Power calculations
• System design
• Process efficiency
• Safe fluid handling