Pressure to head converter

A pump adds energy to a liquid, and engineers measure that energy two ways: as pressure (force per area, in bar, kg/cm² or psi) and as head (height of liquid column, in metres). The two are linked by the liquid’s density: head is pressure divided by density times gravity. Because density varies with the liquid and its temperature, a pressure reading only means something once you know the liquid.

For water at room temperature the conversion is close to 1 bar = 10.2 m. For chemicals the specific gravity changes the picture: the same 4 bar discharge represents 40.8 m on water but only 33.9 m on 50 % caustic soda (SG 1.2). Every pump datasheet and gauge reading should be read with this in mind.

Head h in metres = pressure P in bar × 10.1972 ÷ SG. The constant comes from standard gravity: 10⁵ Pa per bar divided by (1000 kg/m³ × 9.80665 m/s²). Going the other way, pressure P in bar = head h in metres × SG ÷ 10.1972.

The converter applies the formula in both directions and also shows every equivalent pressure unit — bar, kg/cm², psi, kPa and MPa — so a single entry answers nameplate, gauge and spec-sheet readings at once.

Centrifugal pump curves are drawn in metres of head because head is independent of the liquid — a pump rated 40 m delivers 40 m whether pumping water or concentrated acid. The pressure at the discharge flange, however, scales with SG. A PTFE-lined pump moving 98 % sulphuric acid (SG ≈ 1.84) at 40 m head produces 7.4 bar, while the same pump on water produces 4 bar. That is why motor power also scales with SG, and why sizing a chemical pump on pressure alone under-sizes the motor.

Teflow’s chemical pump sizing calculator and pump power calculator build the SG into the calculation automatically, and this converter gives the quick pressure-versus-head answer for existing pumps.

1 bar ≈ 10.2 m water · 1 kg/cm² ≈ 10 m water · 1 psi ≈ 0.70 m water · 1 MPa = 10 bar. On a 50 % NaOH line (SG ≈ 1.5), those become 6.8 m, 6.7 m and 0.47 m per unit. For concentrated sulphuric acid (SG ≈ 1.84), divide the water values by 1.84.

The same table is available instantly in the converter — enter any value and read all six columns.

A discharge gauge on a chemical transfer pump reads pressure, not head. To compare the reading against the pump curve, convert the gauge value to head using the liquid’s SG and compare it with the curve at the operating flow. If the computed head is well below the curve, look for a worn impeller, air in the suction, or a partly closed discharge valve — the classic low-head checklist Teflow’s repair engineers run on every chemical pump.

For pressure-boosting systems feeding RO plants, the same conversion tells you whether the booster is contributing its rated head. Call +91 98251 62709 for a repair or commissioning visit across Gujarat.