Free Calculator · Published October 2026
Feet of Head to PSI Converter: The USGS 2.31 Factor
Put a gauge's pounds per square inch and a driller's feet of water on the same line before anyone adds them as if they were one unit.
Built by SubcontractorHub — the software plumbing contractors use to quote, finance, and run every job.
Book a DemoA Feet of Head to PSI Converter Uses 2.31
This converter follows a note in USGS Open-File Report 67-87. Pressure in pounds per square inch is multiplied by 2.31 feet of water per pound per square inch. Pump sizing, which adds more than this one factor, stays on the well pump size calculator.
A gauge reading or a feet-of-water figure. Not a flow.
Horsepower does not belong in either choice.
Important: All calculator results are ballpark estimates
All calculations are estimates based on historical information and should be verified by the user. This tool is provided as a free service for planning purposes only and is not a substitute for a professional assessment, a supplier quote, or applicable local code requirements.
What the Feet of Head to PSI Converter Is Using
2.31 from the airline note
The open-file note tells a reader how to turn an air-gauge pressure into depth to water. The factor it prints is 2.31 feet of water per pound per square inch. Drawdown in feet, on the next line of that note, is a pressure change in psi times the same 2.31.
It multiplies psi by 2.31 and divides feet of water by 2.31. It does not subtract an airline length, because the visitor may only have the pressure. The airline subtraction stays in the USGS note. It is not hidden inside this result.
Worked examples
Each row is multiplication or division by 2.31. Forty psi is 92.4 feet. Fifty psi is 115.5 feet. Sixty psi is 138.6 feet. The reverse of 23.1 feet is 10 psi.
| Case | psi | Feet of water |
|---|---|---|
| 40 psi | 40 | 92.4 |
| 50 psi | 50 | 115.5 |
| 60 psi | 60 | 138.6 |
| 23.1 feet | 10 | 23.1 |
2.31 is not 0.4336
A different USGS manual, TWRI 8-A3 on submersible pressure transducers, prints a conversion table in which feet of water times 4.336 × 10−1 gives psi at 4°C. That factor is 0.4336 psi per foot. One divided by 2.31 is about 0.4329, not 0.4336. This tool does not swap in 0.433 or 0.4336. If a spec sheet says to use the 4°C factor, follow the spec sheet. Do not call the two factors the same number.
What to write on the job ticket
The entered value, the direction, both results, and the factor 2.31. A pressure-tank cut-in is still a psi setting. The tank volume math stays on the pressure tank sizing calculator. Recovery and specific capacity stay on the well recovery rate calculator. A water treatment dealer who saves the 2.31 note will not add feet to psi on the next visit. This conversion does not state a removal percentage, does not pick a horsepower, and does not say the well passed a county rule.
Frequently Asked Questions
What does this converter change?
It converts pounds per square inch and feet of water using 2.31. A USGS open-file note says to multiply pressure in pounds per square inch by 2.31 feet of water per pound per square inch. The tool does that multiplication and the matching division. It does not size a pump.
Why 2.31 and not 0.433?
The fetched airline note prints 2.31 feet of water per psi. A different USGS transducer manual prints 0.4336 psi per foot of water at 4 degrees Celsius. One divided by 2.31 is not 0.4336. This converter stays on 2.31.
Is this the same thing as total dynamic head?
No. Total dynamic head adds pumping level, elevation, a pressure term, and friction. The well pump calculator is that sum. This page only changes psi into feet of water, or the reverse, with 2.31.
Does 40 psi mean the well passed?
No. Forty pounds per square inch times 2.31 is 92.4 feet of water. That is a unit change. It is not a yield, a cut-in setting, or a pass line.
Can this converter use air pressure or gauge height from a different liquid?
No. The 2.31 factor in the fetched note is feet of water per pound per square inch. It is not a factor for another liquid, and it is not a barometric correction.
Save the 2.31 Factor Next to the Gauge
Psi, feet of water, and the factor you used belong on the customer record.
Get a Free DemoAll calculations are estimates based on historical information and should be verified by the user. This tool is provided as a free service for planning purposes only and is not a substitute for a professional assessment, a supplier quote, or applicable local code requirements. It does not size a pump.