Pump curves, tank elevations, and suction sketches often start from head in feet of water and need pressure in psi. For freshwater at ordinary temperatures a standard teaching conversion is 1 psi ≈ 2.31 feet of head, so psi = head_ft / 2.31 (and head_ft = psi × 2.31). This page focuses on the feet-of-head → psi direction. It is for learning and quick checks—not a substitute for project hydraulics, fluid density corrections, the criteria adopted by your authority having jurisdiction, or review by a licensed design professional. It is not a design stamp and not a PE seal.
How the conversion is used
- Start from a head in feet of freshwater (rated pump head, elevation difference, or suction head sketch).
- Divide by 2.31 to get an approximate pressure in psi.
- Use the result only as a sketch: pump curves, tank elevation, and friction calculations still need the full project method.
- If the fluid is not freshwater, do not use 2.31 without adjusting for specific gravity—this page assumes freshwater.
- Do not treat a conversion alone as a sealed hydraulic acceptance.
Free calculator
Educational approximation only. Freshwater factor 2.31 ft/psi. Nothing you enter leaves your browser. For the reverse direction see the PSI to feet of head calculator. For a height ↔ psi elevation sketch see the elevation pressure calculator. For pump demand vs supply sketches see the fire pump curve check or the Fire Pump & Tank Sizing workbook.
Worked example
115.5 ft of freshwater head: pressure = 115.5 / 2.31 = 50 psi. Going the other way, 50 psi × 2.31 = 115.5 ft. A tank surface 40 ft above a pump datum contributes about 40 / 2.31 ≈ 17.3 psi of static elevation pressure before friction—always check against the adopted edition, manufacturer data, and AHJ, not this page alone.
Next steps: convert the other way with the free PSI to feet of head calculator, convert elevation height and psi with the free elevation pressure calculator, sketch pump demand with the free fire pump curve check, and run full pump and tank tables in the Fire Pump & Tank Sizing workbook ($49). For sprinkler segment friction, use the Sprinkler Pipe Friction Loss workbook ($29).