Calculate water pressure from height in psi or bar (about 0.433 psi per foot), convert pressure back to head, or find pressure at a higher or lower outlet.
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Water Pressure Elevation Formula
Static water pressure changes with vertical height only. Horizontal distance does not matter.
|ΔP| (psi) ≈ 0.4335275 × SG × h (ft)
- ΔP = pressure change in psi
- 0.4335275 = approximate psi per vertical foot for modeled density 1,000 kg/m³ at standard gravity; the calculator uses ρgh with exact unit conversions before rounding
- SG = modeled density divided by 1,000 kg/m³. Presets 1.000, 1.025 and 0.983 are illustrative assumptions; the hot preset approximates density near 60 °C (140 °F). Use supplied SG for known conditions.
- h = vertical height in feet
Rearranged to solve for elevation head:
h (ft) ≈ ΔP (psi) / (0.4335275 × SG)
Final pressure at a second point:
Pfinal,gauge = Pstart,gauge ± ρ g Δz
Use minus when the second point is higher, plus when lower. In SI units, ρ = 1,000 × SG kg/m³ and pressure is in Pa. Standard gravity defaults to 9.80665 m/s² and is editable. For the inverse, use a pressure difference rather than absolute pressure. A negative final gauge pressure is below atmosphere under a continuous-column model; it does not prove a stable filled column or flow at an open outlet. Air entry, venting and vapor-pressure limits are not modeled. These static equations exclude pipe friction, fitting losses, flow velocity, pumps and surge. See OpenStax hydrostatics and pressure reference definitions.
Reference Tables
Pressure-change magnitudes for the explicit SG 1.000 assumption (density 1,000 kg/m³) at standard gravity. Density and gravity assumptions affect the values. Display rounding is four decimals in this reference table.
| Height | Pressure (psi) | Pressure (kPa) | Pressure (bar) |
|---|---|---|---|
| 1 ft | 0.4335 | 2.9891 | 0.0299 |
| 10 ft | 4.3353 | 29.8907 | 0.2989 |
| 25 ft | 10.8382 | 74.7267 | 0.7473 |
| 50 ft | 21.6764 | 149.4533 | 1.4945 |
| 100 ft | 43.3528 | 298.9067 | 2.9891 |
| 1 m | 1.4223 | 9.8066 | 0.0981 |
| 10 m | 14.2233 | 98.0665 | 0.9807 |
How to interpret the static model. A calculated pressure does not by itself establish fixture performance, equipment ratings or local code compliance.
| Model result or input | Interpretation |
|---|---|
| Negative gauge pressure | Below atmospheric pressure under the formal continuous-column model; check venting, air entry and absolute/vapor-pressure limits. |
| Zero gauge pressure | At atmospheric reference pressure; this alone does not imply a flow rate. |
| Positive gauge pressure | Above atmospheric reference; the static value does not establish residual pressure during flow. |
| Equivalent elevation head | A zero-flow pressure-difference balance for the chosen density and gravity. |
| System requirements | Use actual fixture specifications, equipment ratings, hydraulic analysis and applicable local requirements. |
Worked Example
You have 60 psi at the street tap. A second-floor showerhead sits 22 ft above that point. What is the static pressure at the showerhead?
- Pressure-change magnitude at SG 1.000 and standard gravity: approximately 0.4335275 × 22 = 9.5376 psi
- Static gauge pressure at the showerhead: 60 − 9.5376 = 50.4624 psi (50.46 psi to two decimals)
That is before losses during flow. No fixed additional loss is justified without flow rate, pipe dimensions, roughness, fittings and other system conditions; calculate or measure those losses for the actual system.
FAQ
Does pipe diameter change static pressure? No. Static pressure depends only on vertical height and fluid density. Diameter affects flow rate and friction loss, not the standing column pressure.
Why about 0.4335 psi per foot? Applying ρgh with density 1,000 kg/m³, standard gravity 9.80665 m/s², one foot = 0.3048 m and one psi = 6,894.757293168 Pa gives approximately 0.4335275 psi/ft. The common 62.4 lb/ft³ approximation divided by 144 is 0.4333333 psi/ft, so it does not derive exactly 0.4335. Both are rounded reference assumptions.
Should I use hot or cold water settings? Choose density at the actual temperature and water composition. The hot preset assumes SG 0.983 (983 kg/m³), approximately representative near 140 °F, rather than evaluating a temperature-density equation. Whether the difference matters depends on the required accuracy and system.
How high can a given pressure push water? Divide the pressure difference by the derived psi-per-foot coefficient for the chosen density and gravity. At SG 1.000 and standard gravity, 40 psi is equivalent to 92.2663 ft of static head. This is not a guaranteed lift or flow rating; source/outlet references and liquid-column conditions matter.
