Enter static head, pipe length, flow rate, and friction losses to calculate total dynamic head (TDH), pump pressure in PSI, bar, and kPa — and pick the right pump first time.
Enter your system parameters to find total dynamic head and required pump pressure
Static Head & Pipe Parameters
Static Head
Height from source water level to discharge
Total Pipe Length
Suction + discharge pipe combined
Pipe Diameter
Internal diameter of the pipe
Flow Rate
Required volume per hour
Minor Losses
Fittings allowance, % of pipe friction
%
Pipe Material
Sets Hazen-Williams C coefficient
⚠ Please enter valid values greater than zero for Static Head, Pipe Length, Pipe Diameter, and Flow Rate.
WaterTankCalculator.com — Pump Head Pressure Results
Your Results
Total Dynamic Head (TDH)
—
metres (m)
TDH (feet)
— ft
Pressure (PSI)
— psi
Pressure (bar)
— bar
Pressure (kPa)
— kPa
Pipe Friction Loss
— m
Minor Losses
— m
Velocity
— m/s
Flow Rate
— L/min
System Pressure Breakdown
📖 How To Use
How to Use This Pump Head Calculator
Sizing a pump correctly prevents under-powered systems and wasted energy. Follow these steps:
Enter static head
Measure the vertical height from the water level the pump draws from (in a well, the level while pumping) up to the highest discharge point. It is often the biggest part of the head in residential and agricultural systems. Use feet or metres; enter 0 if source and outlet are level.
Enter total pipe length
Add the suction pipe length (pump to water source) and discharge pipe length (pump to delivery point). For a straight run, this is straightforward — for complex routes, add each segment.
Set pipe diameter and material
Internal pipe diameter directly affects velocity and friction loss. Select your pipe material — PVC has the lowest friction (C=150), old steel or concrete the highest (C=100).
Set required flow rate
Enter the flow your system needs. A pump filling a household rooftop tank typically moves about 500–2,000 L/h (2–9 GPM); a whole-house booster is sized for several fixtures at once. Irrigation varies widely by crop and area. Choose GPM, L/h, L/min or m³/h.
Set minor losses percentage
Minor losses account for bends, valves, tees, and fittings. A common rough allowance is 10–20% of the pipe friction; runs with many fittings, check valves and filters can need 30% or more. Enter 0 for none.
Read your results
Total Dynamic Head (TDH) and the flow rate together are the duty point you give to a pump supplier. The calculator also shows the head as PSI, bar and kPa, and the note under the results gives the working in feet.
Pro tip: If the outlet needs pressure — a sprinkler, a fixture or a pressure tank's cut-in setting — add it to the TDH: every 1 psi is 2.31 ft (0.70 m) of head. Then allow a modest margin (around 10%) for ageing pipes and measuring errors, and choose a pump whose curve passes through your flow and head near its best efficiency point. A big oversized margin pushes a centrifugal pump to run off its curve.
📐 The Formula
Pump Head Pressure Formula Explained
Total Dynamic Head (TDH) is the sum of three components — static head, pipe friction loss, and minor losses:
TDH = H_static + H_friction + H_minor
H_static = vertical elevation difference (m)
H_friction = pipe friction head loss (Hazen-Williams)
H_minor = H_friction × (minor_loss_% ÷ 100)
(+ any pressure needed at the outlet, as head: psi × 2.31 = ft)
Hazen-Williams Friction Loss Formula
This calculator uses the Hazen-Williams equation, a standard empirical formula for water in pipes with turbulent flow. In US units it is often written hf (ft per 100 ft) = 0.2083 × (100 ÷ C)1.852 × GPM1.852 ÷ d4.866, with d in inches. The SI form is:
H_f = (10.67 × L × Q^1.852) ÷ (C^1.852 × D^4.87)
L = pipe length (m)
Q = flow rate (m³/s)
C = Hazen-Williams roughness coefficient
D = internal pipe diameter (m)
Rough ranges for orientation only; your own pipe sizes, lengths and flow decide the real figure. In US units, 10–15 m is about 33–49 ft (14–21 psi) and 40–50 m about 130–165 ft (57–71 psi). Fire pumps and sprinkler systems are designed to the local fire code (for example NFPA 20 and 13 in the US, EN 12845 in Europe) by specialists.
🎯 Use Cases
When to Use a Pump Head Calculator
🏠
Residential Water Supply
Sizing a booster pump to raise pressure from a ground-level tank to upper floors or a rooftop tank.
🌱
Agricultural Irrigation
Calculating pump requirements for drip or sprinkler systems across fields with varying elevation.
🏗️
Commercial & Industrial
Designing water distribution for multi-storey buildings, factories, or processing plants.
⛏️
Borehole & Well Pumps
Determining submersible pump specifications based on well depth and required delivery head.
This pump head pressure calculator is most accurate for clean fresh water at normal temperatures (10–25°C). For viscous fluids, hot water systems, or very high-flow turbulent conditions, consult a hydraulic engineer for additional correction factors.
🧮 Worked Example
Worked example: pumping to a tank 30 ft up
A pump fills a tank whose inlet is 30 ft (9.14 m) above the water level in the source tank, through 120 ft (36.6 m) of 1-inch Schedule 40 PVC (inside diameter 1.049 in, 26.6 mm). You want 10 GPM (37.9 L/min) and allow 20% for fittings.
Static head: 30 ft.
Pipe friction (Hazen-Williams, C = 150): 6.6 ft (2.00 m); the water moves at 3.7 ft/s (1.13 m/s).
Fittings: 20% × 6.6 = 1.3 ft.
Total dynamic head: 30 + 6.6 + 1.3 = 37.9 ft (11.55 m), the same as 16.4 psi (1.13 bar).
So you need a pump whose curve gives at least 10 GPM at about 38 ft. Flow matters a lot: at 20 GPM in the same pipe, friction jumps to 23.7 ft and the TDH to about 58 ft — or move up to 1¼-inch pipe. The pump horsepower calculator turns 10 GPM at 38 ft into a motor size.
❓ FAQ
Frequently Asked Questions
What is total dynamic head (TDH) and why does it matter?
Total Dynamic Head (TDH) is the total equivalent height that a pump must lift water against, accounting for actual vertical elevation plus all friction losses in the pipes and fittings, plus any pressure needed at the outlet. It is the single most important number for pump selection — a pump's performance curve plots flow rate against head, and your operating point must fall on that curve. Underestimating TDH leads to insufficient flow; overestimating it leads to a bigger pump than needed that wastes energy and runs away from its best efficiency point.
How do I calculate pump head pressure manually?
To calculate pump head manually: (1) measure the static head — the vertical height from water source to discharge; (2) calculate pipe friction loss using the Hazen-Williams formula H_f = (10.67 × L × Q^1.852) ÷ (C^1.852 × D^4.87); (3) add minor losses — commonly 10–20% of friction head for bends and fittings; (4) add any pressure needed at the outlet (psi × 2.31 = ft); (5) sum them: TDH = Static Head + Friction Loss + Minor Losses + Outlet Pressure Head. This calculator does all that automatically.
What is the difference between static head and total dynamic head?
Static head is just the vertical elevation difference between the water source and the delivery point — a fixed physical measurement. Total dynamic head (TDH) is static head plus all the additional pressure loss caused by water flowing through pipes, bends, valves, and fittings. TDH is always larger than static head — by a little on a short, wide pipe at low flow, or by more than the static head itself on a long, narrow pipe at high flow.
How do I convert pump head (metres) to pressure (PSI or bar)?
To convert pump head in feet to pressure, multiply by 0.433 to get psi (100 ft = 43.3 psi). For head in metres, multiply by 0.09807 to get bar, by 1.4223 to get psi, or by 9.807 to get kPa. For example, 20 m TDH = 1.96 bar = 28.4 psi = 196 kPa. These conversions assume fresh water at standard gravity (9.807 m/s²).
What percentage should I use for minor losses?
Minor losses (from bends, elbows, tees, valves, and entry/exit losses) are typically expressed as a percentage of the friction head loss. As rough rules of thumb: about 10% for simple systems with very few fittings, 15–20% for standard residential or irrigation systems, and 25–30% or more for systems with many bends, check valves, filters and reducers. For a short pipe crowded with fittings the percentage method can undercount — then add each fitting's equivalent pipe length instead.
Why does pipe diameter affect pump head so dramatically?
Pipe diameter has an outsized effect because friction loss is inversely proportional to diameter raised to the power of 4.87 in the Hazen-Williams equation. Halving the pipe diameter increases friction loss by a factor of roughly 29 at the same flow rate (24.87). This is why upgrading from a 25 mm to a 32 mm pipe can dramatically reduce the pump head required — and potentially allow a smaller, cheaper pump to do the same job.
What pump head do I need for a rooftop water tank?
For a typical two-storey home with a rooftop tank 6–8 metres above the pump, and 20–30 metres of pipe, you typically need a TDH of 12–20 metres (1.2–2.0 bar / 17–29 PSI). For a five-storey building, expect 25–35 metres TDH. Allow a modest margin (around 10%) and select a pump whose curve passes through your flow and head near its best efficiency point (BEP) — the Hydraulic Institute's preferred operating region is usually about 70–120% of BEP flow.
Can I use this calculator for submersible borehole pumps?
Yes. For a submersible borehole pump, the static head is the total vertical lift from the pumping water level (the water level when the pump is running, not the static water level) to the discharge point. Enter the depth from the surface down to the pumping water level, plus the above-ground delivery height, as the static head — not the depth the pump is set at. The friction loss calculation works the same way for the discharge pipe. Many borehole applications end up with a TDH of 40–80 metres (130–260 ft), and a pressure-tank system also needs the tank's cut-off pressure added (for example, 50 psi = 115 ft).
✅ Sources & Review
Sources and review
The method and figures on this page come from these references:
Hazen-Williams friction loss, Hf = 10.67 L Q1.852 ÷ (C1.852 D4.87) in SI units, as given in standard water-supply hydraulics texts.
Toro Agricultural Irrigation — Hazen-Williams Equation: C values by pipe material and the US form of the equation.
Hydraulic Institute preferred operating region (POR): usually 70–120% of best-efficiency-point flow — summarised by Intro to Pumps.
NIST SP 811 — unit conversions (1 psi = 2.31 ft = 0.703 m of water; 1 US gallon = 3.785 L).
Schedule 40 PVC inside diameters per ASTM D1785 dimensions (1" 1.049 in, 1¼" 1.380 in).
Reviewed by John Mac, PE, Water Systems Specialist
Texas-licensed Professional Engineer with 13+ years in residential water storage and 180+ tank projects. John writes and reviews every calculator on this site.
