Feet of Head & Water Column to PSI Converter
Convert PSI to feet of head, water column to PSI, kPa and bar in either direction. For pump sizing, water pressure, and static head calculations in plumbing and HVAC systems.
1 PSI = 2.31 feet of head = 27.7 in. water column
Pressure & Head Converter
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ft head
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in. WC
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Quick conversions:
Feet of Head to PSI Conversion Chart
| Feet of Head | PSI | In. Water Column | kPa | Bar |
|---|---|---|---|---|
| 1 | 0.4329 | 11.99 | 2.98 | 0.0298 |
| 5 | 2.16 | 59.97 | 14.92 | 0.1492 |
| 10 | 4.33 | 119.9 | 29.85 | 0.2985 |
| 20 | 8.66 | 239.9 | 59.69 | 0.5969 |
| 30 | 12.99 | 359.8 | 89.54 | 0.8954 |
| 46 | 19.91 | 551.8 | 137.3 | 1.37 |
| 50 | 21.65 | 599.7 | 149.2 | 1.49 |
| 69 | 29.87 | 827.6 | 205.9 | 2.06 |
| 100 | 43.29 | 1,199.5 | 298.5 | 2.98 |
| 150 | 64.94 | 1,799.2 | 447.7 | 4.48 |
| 231 | 100 | 2,770.8 | 689.5 | 6.89 |
Values are for cold water (about 60 °F / 15 °C). Hot water is slightly less dense, so a given column height produces marginally less pressure.
Inches of Water Column to PSI
One inch of water column is 0.0361 PSI, and 1 PSI is 27.708 inches of water column. To convert water column to PSI, multiply inches of WC by 0.0361; to go the other way, multiply PSI by 27.708. The numbers are small because water column is the unit used where pressures are far below 1 PSI.
That is why you meet it in two places in particular. Natural gas piping is sized and tested in inches of water column — a typical residential appliance manifold runs around 3.5" WC for natural gas and about 11" WC for propane, which is 0.13 PSI and 0.40 PSI respectively. HVAC duct static pressure is also read in inches of WC, where a residential system commonly sits near 0.5" WC, or 0.018 PSI. Reading those figures as PSI without converting is the mistake that makes a gas pressure test look wildly wrong.
| Inches of WC | PSI | Where you see it |
|---|---|---|
| 0.5" | 0.018 | Residential duct static pressure |
| 3.5" | 0.126 | Natural gas appliance manifold |
| 11" | 0.397 | Propane appliance manifold |
| 27.708" | 1.000 | Definition: 1 PSI |
PSI to Feet of Head
To convert PSI to feet of head, multiply by 2.31. So 40 PSI is 92.4 feet of head, 60 PSI is 138.6 feet, and 80 PSI is 184.8 feet. This is the direction you need when a pump curve is published in feet but your system pressure is measured in PSI, which is the usual mismatch on a domestic booster or well pump.
Read it as a height and the arithmetic stops being abstract: 1 PSI lifts fresh water 2.31 feet, so a 50 PSI supply can in principle raise water about 115 feet before flow stops. For any fluid other than fresh water, divide 2.31 by the specific gravity — a 50 percent glycol mix near 1.07 gives 2.16 feet per PSI, so the same pressure reaches roughly 8 feet less.
Feet of Head ↔ PSI Formula
Feet of Head to PSI
PSI = Feet ÷ 2.31
Example: 100 ft ÷ 2.31 = 43.3 PSI
PSI to Feet of Head
Feet = PSI × 2.31
Example: 60 PSI × 2.31 = 138.6 ft
The factor 2.31 comes from the weight of water: 1 PSI is the pressure at the bottom of a 2.31-foot column of water. It applies to fresh water; for other fluids, divide 2.31 by the fluid's specific gravity.
Inches of water column: 1 PSI = 27.708 in. WC. This unit is common for low-pressure gas piping and duct static pressure.
Can You Convert PSI to GPM?
No — PSI (pressure) and GPM (flow rate) are different quantities, so there is no single conversion factor. Flow depends on pressure and pipe size, length, and fittings. Two systems at the same 60 PSI can deliver very different GPM depending on the pipe.
To find flow from pressure, use the pipe dimensions with our water flow rate calculator or account for pressure loss along the run with the friction loss calculator.
Frequently Asked Questions
How many feet of head is 1 PSI?
1 PSI equals 2.31 feet of head (feet of water column) for fresh water. So a pressure of 40 PSI is equivalent to about 92.4 feet of head, and 60 PSI is about 138.6 feet.
How do you convert feet of head to PSI?
Divide the feet of head by 2.31. For example, 100 feet of head ÷ 2.31 = 43.3 PSI. This works because a 2.31-foot column of water exerts exactly 1 PSI at its base.
What is water column pressure and how does it convert to PSI?
Water column (WC) measures pressure as the height of a water column. 1 PSI = 27.708 inches of water column, and 1 inch of WC = 0.0361 PSI. Inches of water column are widely used for natural gas piping and HVAC duct static pressure, where pressures are very low.
Why is the conversion factor 2.31?
Water weighs 0.433 pounds per square inch for every foot of height. The reciprocal of 0.433 is 2.31, so 1 PSI supports a 2.31-foot column of fresh water. For fluids other than water, divide 2.31 by the fluid's specific gravity.
How much PSI does elevation add to a water system?
Every foot of elevation drop adds 0.433 PSI of static pressure (and every foot of rise subtracts it). So a water tank 100 feet above a fixture provides 43.3 PSI of static pressure before any flow losses. This is why pump total dynamic head is often expressed in feet.