Pump Sizing Calculator
Calculate total dynamic head from lift, friction and pressure.
How this calculator works
TDH = static lift + (pipe length × friction ÷ 100) + (psi × 2.31)
One psi equals 2.31 feet of head for water. Pump curves plot flow against head, so you select a pump by finding where your required flow and TDH intersect on its curve.
Switch the site to metric — the control is in the footer — and your inputs, your results and the tables below follow. The formula, the constants, the guidance text and the sources stay in US units on purpose: that is how the standards they come from are written, and restating them would detach each figure from the document you are meant to be able to check it against.
Where these numbers come from
- Hydraulic Institute ANSI/HI 9.6.7 (Rotodynamic Pumps — Effects of Liquid Viscosity) 2021 — total dynamic head as static lift plus friction plus pressure head
- NIST Special Publication 811 2008 — one psi as 2.31 feet of water head at standard conditions
Standards are revised on a cycle. The edition above is the one this figure was checked against — confirm it against the edition your jurisdiction has adopted.
Worked example
With static lift 50 ft, total pipe length 200 ft, friction loss per 100 ft 3 ft, required pressure at outlet 40 , this calculator returns 148.4 ft.
Total dynamic head for common pump duties
Click through any row to load those measurements. The address bar keeps them, which makes the result something you can paste into a message.
| Job | Size | Total dynamic head |
|---|---|---|
| Shallow well to house | 25 ft × 100 ft × 3 ft × 40 | 120.4 ft |
| Deep well | 180 ft × 250 ft × 3 ft × 50 | 303.0 ft |
| Pond to irrigation | 20 ft × 400 ft × 4 ft × 30 | 105.3 ft |
| Basement sump to grade | 12 ft × 40 ft × 5 ft × 0 | 14.00 ft |
| Booster for upper floor | 30 ft × 80 ft × 3 ft × 60 | 171.0 ft |
Select where your required flow and this head cross on the pump curve, not from the horsepower on the box.
Frequently asked questions
What is total dynamic head?
The total resistance a pump must overcome: the vertical lift, plus friction losses in the pipe, plus any pressure required at the outlet. It is the number you match against the pump curve.
How do I convert PSI to feet of head?
Multiply by 2.31 for water. Forty psi at the outlet is equivalent to 92.4 ft of head, which on most residential systems is the largest single component of TDH.
Does pipe size affect pump sizing?
Substantially, through friction. Going up one pipe size can cut friction loss by half or more, which often lets you fit a smaller pump — usually cheaper than the larger pump over the system lifetime.
What happens if a pump is oversized?
It runs off the right-hand end of its curve, cavitates, wastes energy and wears the impeller and seals. Pumps are efficient only near their best efficiency point, so accurate TDH matters both ways.