Specific Speed (N_s)

The geometry, or shape, of a pump impeller. The formula for specific speed (N_s) is:

For US Units:

N is pump speed in rpm; Q is capacity in gallons per minute at the best efficiency point; and H is total head in feet per stage at the best efficiency point.

For Metric Units:

N is pumps speed in rpm; Q is capacity in liters per second at the best efficiency point; and H is total head in meters per state at the best efficiency point.

Use the following relationships to convert N_s values between those with US units, Imperial units (gpm), metric units (m³/h, L/s) and vice versa:

N_{s(US gpm, ft.)} = 0.861 N_{s(m³/h, m)}

N_{s(British gpm, ft.)} = 0.787 N_{s(m³/h, m)}