Water Pressure Calculator Online - Hydrostatic Pressure, Pump Head & Force

Water Depth (below surface)

Water Type

Convert

Pressure

Head (water column)

Pressure

Area Input

Diameter

Area

Formulas

Hydrostatic Pressure

        P = ρ × g × h
      

ρ = water density (998.21 kg/m³ fresh at 20 °C, 1025 kg/m³ seawater), g = 9.80665 m/s², h = depth below the free surface. Result is gauge pressure — add 1 atm (1.013 bar) for absolute pressure.

Pressure ↔ Head

        h = P / (ρ × g)
      

Pump head is the energy per unit weight, expressed as an equivalent column of water. At 20 °C, 1 bar ≈ 10.21 m of head; 1 psi ≈ 0.703 m.

Force from Pressure

        F = P × A   (circle: A = π × d² / 4)
      

Conversions Used

1 bar = 100 kPa = 0.1 MPa = 14.5038 psi = 0.98692 atm
1 atm = 101,325 Pa; 1 ft = 0.3048 m; 1 inch = 25.4 mm
1 N = 0.101972 kgf = 0.224809 lbf

FAQ

How much pressure is 1 metre of water?

At 20 °C, one metre of fresh water column produces P = ρgh = 998.21 × 9.80665 × 1 = 9,789 Pa ≈ 0.0979 bar ≈ 1.42 psi. The common rule of thumb "1 bar per 10 m" is accurate to about 2%. Seawater (1025 kg/m³) gives roughly 0.1005 bar per metre.

What is the pressure at 10 m depth?

Gauge pressure at 10 m in fresh water at 20 °C is 0.979 bar (14.2 psi); in seawater it is 1.005 bar. If you need absolute pressure (e.g. for dissolved-gas calculations), add atmospheric pressure: 0.979 + 1.013 = 1.992 bar absolute.

How do I convert bar to metres of head?

Divide the pressure by ρg: h = P / (ρ × g). For water at 20 °C, 1 bar = 100,000 / (998.21 × 9.80665) = 10.21 m. So 3 bar ≈ 30.7 m of head, and a pump rated 50 m head develops about 4.9 bar. The Head tab does this in both directions.

Does hydrostatic pressure depend on container shape?

No — this is the hydrostatic paradox. Pressure at a point depends only on the depth below the free surface and the fluid density, not on the volume or shape of the container. A thin tube and a wide lake produce the same pressure at 5 m depth.

How much force does water pressure exert on a surface?

F = P × A for a uniform-pressure surface (small area or piston). Example: 6 bar acting on a 200 mm hydraulic piston (A = 0.0314 m²) produces F = 600,000 × 0.0314 ≈ 18.8 kN ≈ 1,920 kgf — the working principle of hydraulic presses. For tall submerged walls use the average depth (pressure at the centroid) or integrate: F = ρg·h̄·A.

Why does temperature barely change hydrostatic pressure?

Water density varies less than 4% between 0 °C and 100 °C (999.8 → 958.4 kg/m³), so pressure at depth changes proportionally little. The calculator offers 4 °C (maximum density), 20 °C and 60 °C for hot-water circuits. Seawater is denser due to salt (~1025 kg/m³), adding about 2.7% pressure at the same depth.

How to Use the Water Pressure Calculator

Hydrostatic tab: enter the depth below the water surface and pick the water type — get gauge pressure in bar, kPa, psi and atm immediately.
Pressure ↔ Head tab: convert a pump's pressure rating into metres (or feet) of head, or a head value into pressure — essential for pump selection.
Pressure Force tab: enter pressure plus a circular diameter (or any custom area) to get the thrust on pistons, covers, flanges and walls.
Copy link saves your inputs in the URL; tap the depth pills for quick references like 2 m, 10 m or 100 m.

Understanding Water Pressure, Head and Force

Hydrostatic pressure is the weight of the fluid column above a point: P = ρgh. It grows linearly with depth at roughly 0.098 bar per metre of fresh water — the familiar "1 bar per 10 m" used by divers (who indeed experience about 2 bar absolute at 10 m, atmospheric included) and by submersible-pump installers sizing discharge heads. Remarkably, the shape and total volume of the container play no role (the hydrostatic paradox): a 10 m deep well and a 10 m deep ocean exert the same pressure at the bottom. Density sets the proportionality: seawater at 1025 kg/m³, warm fresh water slightly less (965 kg/m³ at 90 °C).

Pump head rewrites pressure as an equivalent column height, h = P/(ρg), because a pump's energy output is naturally measured per unit weight of fluid. At 20 °C, 1 bar corresponds to 10.21 m of water; a typical domestic booster delivering 3 bar adds about 30.7 m of head, while the same pump on denser seawater or lighter gasoline produces different pressures from the identical head rating. Always match the fluid when converting — the Head tab uses fresh water at 20 °C by convention and lets you verify round-trip consistency.

Force is pressure times area: F = P·A. Doubling a hydraulic piston's diameter quadruples the force, which is why hydraulic presses scale so effectively — 6 bar on a modest 200 mm bore already yields nearly 19 kN (about 1.9 tonnes). For large submerged surfaces (dams, tank walls, gates), pressure varies with depth; use the pressure at the centroid times the area, or integrate the triangular distribution — the exact resultant acts at two-thirds depth for rectangular walls.

Water Pressure Calculator