Fluid Velocity to Velocity Head Calculator

This calculator converts average fluid velocity into velocity head, or velocity head back into fluid velocity. Choose the quantity to calculate, enter the other one, and the result updates immediately. Velocity head is the kinetic-energy term in the Bernoulli equation and is expressed as a length of the flowing fluid.

The formulas

To calculate velocity head, use Hv = Vf²/(2g). To reverse the calculation, use Vf = √(2gHv). Here Vf is average fluid velocity and g is standard gravitational acceleration: 32.174 ft/s² in US customary units or 9.80665 m/s² in SI.

Why density does not appear

Velocity head is kinetic energy per unit weight. Density cancels when the kinetic-energy term is divided by specific weight, so the same velocity produces the same velocity head for water, oil, or another liquid when the velocity and gravitational acceleration are the same. Density matters when converting head to pressure, but not when converting velocity to head.

Use average section velocity

Enter the bulk average velocity at the cross-section of interest. A real pipe has a velocity profile, but most pump and piping calculations use average velocity Q/A. If only flow and inside diameter are known, first use the Pipe Size & Velocity Calculator.

Worked example

For a fluid moving at 10 ft/s, velocity head is 10² ÷ (2 × 32.174) = 1.554 ft. The same physical case is 3.048 m/s and 0.4737 m of velocity head. Reversing the formula with either head value returns the original velocity.

Where velocity head is used

Velocity head is one term in total head and in the Bernoulli energy equation. It is also the base term in the fitting-loss relation HL = K · V²/(2g). Add it to a complete energy balance only when the inlet and outlet velocity heads differ; if both pipe velocities are equal, their difference is zero.