Interactive Calculator · 2026
Water Pressure Calculator
Convert a water column height into pressure. Enter the head — the vertical height of an overhead tank above the tap — and see the pressure it produces in bar, kPa and psi. This is the static pressure before friction losses in the pipe.
Pressure at the tap for tank heights of 3, 6, 10 and 20 m
Your water column
Vertical distance from the water surface in the overhead tank down to the outlet. Each floor adds roughly 3 m of head.
How tank height drives pressure
Pressure rises in direct proportion to the height of the water above the tap.
About 1 m of head ≈ 0.098 bar. A single storey (~3 m) gives only about 0.29 bar — weak, trickly flow at the tap. That is why overhead tanks need real height, or a pressure pump, to drive showers and geysers properly.
This is the static pressure with no flow. Once water moves, friction in the pipes and fittings eats into it — verify the actual pressure at the tap with a gauge.
How this is calculated
- Pressure = ρ × g × head, with ρ = 1000 kg/m³ (water) and g = 9.81 m/s². This gives pressure in pascals, which we convert to the familiar units below.
- Pressure (bar) = head × 0.0981 = 10 × 0.0981 = 0.981 bar.
- Pressure (kPa) = head × 9.81 = 10 × 9.81 = 98.1 kPa.
- Pressure (psi) = head × 1.4223 = 10 × 1.4223 = 14.223 psi.
Indicative figures for concept planning — the static head pressure with no flow. Actual delivered pressure is lower once friction losses are included; confirm with a gauge and a qualified consultant (NBC 2016 Part 9) before sizing pumps or fixtures.
Frequently asked questions
- How does the water pressure calculator convert tank height to pressure?
- It uses the static head formula: pressure equals water density times gravity times height, with density 1000 kg per cubic metre and gravity 9.81. In practice each metre of head produces about 0.098 bar. Enter the vertical height of the water column and the tool returns the pressure in bar, kPa and psi. This is the pressure with no water flowing.
- What height should I enter for the head?
- Enter the vertical distance from the water surface in your overhead tank down to the tap or fixture, in metres, not the horizontal pipe length. In an Indian home each floor adds roughly 3 m of head, so a tank on a terrace above a ground-floor tap is often 9 to 12 m. Measure or estimate the true vertical drop for a realistic figure.
- Why is my actual tap pressure lower than this result?
- This tool gives static head pressure, meaning the pressure when no water is moving. Once a tap opens, friction in pipes, bends, valves and fixtures reduces the delivered pressure, sometimes sharply on long or narrow runs. Treat the number as an indicative planning figure, verify the real pressure at the tap with a gauge, and consult NBC 2016 Part 9 or a plumber before sizing pumps or fixtures.
Related Guides — Deep-dive reading
Gravity-Fed Plumbing System in India: How Overhead Tanks Push Water to Every Tap
The overhead-tank-to-fixture model that most Indian homes run on — how head height creates pressure, why the tank sits on the roof, how much pressure each floor really gets, how to size pipes for gravity flow, and exactly where gravity struggles and how to fix it.
PlumbingOverhead Water Tank on the Roof (India): Why It's Up There, Sizing, Structural Load, Fittings & Care
The rooftop tank is what gives your taps and showers their pressure. Why height creates head, how to size it, what a full tank weighs and how to support it on the slab, materials, staging height, overflow and vent, sun and algae, cleaning access, and when to run more than one tank.
PlumbingLow-Rise Plumbing Systems in India: Houses, Villas & Buildings up to 4 Storeys
How plumbing is organised for independent houses, villas and low-rise buildings up to about four storeys — the simple overhead-tank gravity model, when a small booster is still worth adding, single- versus multi-floor distribution, and the simpler stack and venting a low building can get away with.
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