Calculate total dynamic head from static head, friction loss, vessel pressure, and velocity head — in feet and metres, with the formula and a component breakdown shown.
K is the pressure-to-head constant: 2.31 ft per psi (US) or 10.2 m per bar (SI), for water at SG = 1.
For preliminary sizing and educational use. Verify final design against manufacturer performance curves and applicable codes; final designs should be reviewed by a licensed professional engineer.
Total dynamic head (TDH) is the total equivalent height a pump must raise the fluid, combining static lift, friction loss, and any difference in vessel pressure. It is the head value you take to a pump curve to select a pump. Total dynamic head equals static head plus friction loss plus pressure head, measured in feet or metres.
Worked example
A pump draws from an open tank below the pump (a 10 ft suction lift) and discharges to a vessel 120 ft above it that is pressurised to 30 psig. Suction-line friction loss is 3 ft; discharge-line friction loss is 25 ft; the fluid is water (SG = 1.0).
Static head: 120 − (−10) = 130 ft
Friction loss: 25 + 3 = 28 ft
Pressure head: (30 − 0) × 2.31 / 1.0 = 69.3 ft
TDH = 130 + 28 + 69.3 = 227 ft (69.3 m)
When to use — and when not to
Use TDH to find the head your system demands at the design flow, then read that duty point against a manufacturer’s pump curve. TDH is a single-flow figure: friction loss rises with the square of flow, so a full system curve is needed to see the operating point across a flow range. This calculator assumes friction losses are supplied (compute them with the friction-loss calculator) and that the fluid is Newtonian.
Frequently asked questions
Is suction lift positive or negative?
When the source is below the pump (a lift), the static suction head is negative, which increases TDH. When the source is above the pump (a flooded suction), it is positive and reduces TDH. This calculator handles the sign for you through the “source above / below pump” selector.
Where does the 2.31 come from?
2.31 converts psi to feet of head for water (SG = 1): one psi supports about 2.31 ft of a water column, since 144 in²/ft² ÷ 62.4 lb/ft³ ≈ 2.31. For other fluids, divide by specific gravity. In SI the equivalent is 10.2 m per bar.
