PSI to Feet of Head Converter
Convert psi to feet of head (or feet of water): pressure in psi to the height of liquid column it supports. For water, multiply psi by 2.31. For any other liquid, divide by its specific gravity as well, which the converter does when you choose the liquid or enter its SG.
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How It Works
Head is pressure expressed as the height of a column of liquid that would produce it. Pump curves are drawn in feet of head because a centrifugal pump lifts any thin liquid to the same height at a given flow and speed, whatever its density. The pressure that height produces does depend on density, so converting between psi and feet needs the specific gravity (SG) of the liquid.
A gauge reading in psi becomes feet of head by dividing the pressure by the liquid's specific weight: h = P / (ρ × g). On the conventional water basis of 1,000 kg/m³ and standard gravity, 1 psi supports 2.30666 ft of water. A denser liquid stands lower for the same pressure and a lighter one stands higher.
Formula
Feet of head = psi × 2.30666 ÷ SG
The 2.30666 factor uses the conventional water column (1,000 kg/m³, 9.80665 m/s²), the basis of the ftH2O unit in unit tables. Water at 60 °F (SG 0.9990) gives 2.30897 ft per psi. Both round to the 2.31 used in pump formulas and handbooks.
Worked Example
A gauge on a loop filled with a glycol mix of SG 1.04 reads 45 psi:
45 × 2.30666 ÷ 1.04 = 99.8074 ft of head
PSI to Feet of Head Table (water, SG 1.0)
| psi | ft | m |
|---|---|---|
| 1 psi | 2.30666 ft | 0.70307 m |
| 2 psi | 4.61332 ft | 1.40614 m |
| 5 psi | 11.5333 ft | 3.51535 m |
| 10 psi | 23.0666 ft | 7.0307 m |
| 15 psi | 34.5999 ft | 10.546 m |
| 20 psi | 46.1332 ft | 14.0614 m |
| 30 psi | 69.1998 ft | 21.0921 m |
| 40 psi | 92.2663 ft | 28.1228 m |
| 50 psi | 115.333 ft | 35.1535 m |
| 60 psi | 138.4 ft | 42.1842 m |
| 80 psi | 184.533 ft | 56.2456 m |
| 100 psi | 230.666 ft | 70.307 m |
| 150 psi | 345.999 ft | 105.46 m |
Feet of Head per PSI by Liquid
The same 1 psi gives a different height of column for each liquid. For a liquid not listed, take its SG from the supplier datasheet and enter it above.
| Liquid | 1 psi |
|---|---|
| Water, conventional (SG 1.000) | 2.30666 ft |
| Water at 60 °F / 15.6 °C (SG 0.9990) | 2.30897 ft |
| Water at 20 °C / 68 °F (SG 0.9982) | 2.31082 ft |
| Water at 60 °C / 140 °F (SG 0.9832) | 2.34607 ft |
| Water at 80 °C / 176 °F (SG 0.9718) | 2.37359 ft |
| Seawater (SG 1.025) | 2.2504 ft |
SG here is relative to 1,000 kg/m³. A datasheet SG referenced to water at 60 °F differs by 0.1%, which you can ignore.
Going the other way? Use the feet of head to psi converter. To size a pump from the lift, pipe friction and outlet pressure, use the total dynamic head calculator.
FAQ
Common questions about converting psi to feet of head.
Frequently Asked Questions
How do I convert psi to feet of head?
Multiply psi by 2.30666 for water. For example, 50 psi × 2.30666 = 115.333 ft of head. For another liquid, divide the result by its specific gravity.
How many feet of head is 1 psi?
1 psi equals 2.30666 feet of water column on the conventional basis (SG 1.0). With water at 60 °F it is 2.30897 ft. The rounded figure used in pump formulas and handbooks is 2.31.
Why do pump curves use feet of head instead of psi?
A centrifugal pump adds the same head to any thin liquid at a given flow and speed, so one curve in feet holds for water, brine and most glycol mixes. The pressure rise in psi depends on the liquid's density, so a curve drawn in psi would only be right for one fluid. Viscous liquids such as oils lower both head and flow, and the curve then needs a viscosity correction (ANSI/HI 9.6.7).
Does pipe size change the conversion?
No. Pressure and head convert through the liquid's density and gravity alone. Pipe size changes how much head is lost to friction along the pipe, which is a separate calculation.
Is feet of head the same as feet of water?
For water, yes. Feet of water (ftH2O, ft w.c.) is head measured in water. Feet of head is the general term for any liquid, which is why the specific gravity matters when the liquid is not water.
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