Fire pumps, tanks, and elevation sketches often move between pressure in psi and head in feet of water. For freshwater at ordinary temperatures a standard teaching conversion is 1 psi ≈ 2.31 feet of head (equivalently head_ft = psi × 2.31, and psi = head_ft / 2.31). This page explains that sketch and gives a free browser calculator that converts both directions. 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.
How the conversion is used
- Decide whether you have a pressure (psi) to turn into head (ft), or a head (ft) to turn into pressure (psi).
- For freshwater, multiply psi by 2.31 to get feet of head, or divide feet of head by 2.31 to get 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 (for example antifreeze solutions or other densities), 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. Net positive suction head, rated pump head, and elevation differences still belong in a complete calculation.
Free calculator
Educational approximation only. Freshwater factor 2.31 ft/psi. Nothing you enter leaves your browser. For pump demand vs supply sketches see the fire pump curve check or the Fire Pump & Tank Sizing workbook. For pipe friction after you know flow and size, see the Hazen-Williams calculator or the Sprinkler Pipe Friction Loss workbook.
Worked example
50 psi of freshwater pressure: head = 50 × 2.31 = 115.5 ft. Going the other way, 115.5 ft of head ÷ 2.31 ≈ 50 psi. 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: sketch pump demand with the free fire pump curve check, estimate available supply with the hydrant flow test calculator or residual pressure calculator, and run full pump and tank tables in the Fire Pump & Tank Sizing workbook. For sprinkler segment friction, use the Sprinkler Pipe Friction Loss workbook.