Calculate total dynamic head or solve for static head, friction loss, or required pressure in feet, meters, PSI, kPa, and bar for pump sizing.

Add known head components at the same design flow. Enter each loss once.

Discharge elevation minus supply elevation; a lower discharge is negative.

1 uses a reference density of 1,000 kg/m³; use the fluid’s actual specific gravity.

System allowances and display

Discharge velocity head minus supply velocity head; this difference may be negative.

Pressure head only. Supply elevation is already included in the static difference.

TDH – Total Dynamic Head – Formula

The following formula is used to calculate a total dynamic head:

TDH = PH + FLH + EH
  • Where TDH is the total dynamic head (ft)
  • PH is the pressure head (ft)
  • FLH is the friction head loss (ft)
  • EH is the elevation head

For the simple case shown, sum pressure head, friction head loss and discharge-minus-supply elevation difference. The calculator also includes optional minor losses and a signed velocity-head difference, and subtracts existing supply pressure head. Use consistent reference points and count each component once.

TDH Definition

TDH is the head a pump must add at the design flow to satisfy the elevation, pressure and loss balance for a steady incompressible fluid. This component balance does not calculate pipe losses or select a pump curve.

The simple balance uses three components; optional allowances account for minor losses, velocity-head difference and supply pressure:

Elevation Head: Discharge elevation minus supply elevation. A lower discharge can give a negative difference.

Pressure Head: Pressure divided by fluid density and gravitational acceleration. Density is modeled as 1,000 times specific gravity kg/m³, with g = 9.80665 m/s². Existing supply pressure head is subtracted separately; do not include supply elevation in that field.

Friction Loss Head: Head lost to pipe friction at the design flow. Enter fitting losses separately only when they are not already included in this value.

Example Problem

How to calculate the total dynamic head?

First, determine the elevation head. For this example, the pump must overcome 100 ft of elevation.

Next, determine the pressure head. In this case, the pressure head is found to be 12ft.

Next, determine the friction loss head. The total friction loss is an equivalent head of 10ft.

Finally, calculate the TDH using the formula above:

TDH = PH + FLH + EH

TDH = 100 + 12 + 10

TDH = 122 ft of total head

FAQ

What is the importance of calculating Total Dynamic Head (TDH) in a pumping system?
TDH identifies the head requirement at a specified flow. Compare that operating point with the pump curve and separately verify power, efficiency and NPSH; head alone does not establish that a pump is suitable.

How can elevation affect the Total Dynamic Head in a system?
Elevation affects TDH by adding to the height that the pump needs to lift the fluid. Higher elevations require the pump to work harder to overcome gravitational forces, increasing the TDH. This is especially significant in systems where fluids are pumped from lower to higher levels.

Can the Total Dynamic Head change over time, and what factors contribute to such changes?
Yes, the TDH can change over time due to several factors, including pipe wear leading to increased friction losses, changes in system elevation due to construction or modifications, and variations in pressure requirements based on system demand. Regular system evaluations are necessary to ensure optimal pump performance.