Liquid height h = P ÷ (ρ × g). For water: h (m) ≈ P (kPa) ÷ 9.81 or P (bar) × 10.2. Enter the pressure and the liquid density below to get the level, or enter a level to get the transmitter range you need.
Hydrostatic level calculator
Standard gravity gₙ = 9.806 65 m/s² (NIST CODATA). Densities are typical values — use your liquid's density at process temperature for best accuracy.
The hydrostatic level formula
h = P ÷ (ρ × g) — h: liquid height above the sensor diaphragm (m); P: gauge pressure (Pa); ρ: liquid density (kg/m³); g: 9.806 65 m/s².
P = ρ × g × h — use this to choose the transmitter range for a tank of known height.
Pressure-to-level table
| Pressure | Water (998 kg/m³) | Seawater (1025) | Diesel (840) |
|---|---|---|---|
| 0.1 bar (10 kPa) | 1.02 m | 0.99 m | 1.21 m |
| 0.5 bar (50 kPa) | 5.11 m | 4.97 m | 6.07 m |
| 1 bar (100 kPa) | 10.22 m | 9.95 m | 12.14 m |
| 2 bar (200 kPa) | 20.43 m | 19.90 m | 24.28 m |
Sizing a submersible level transmitter
- 1Find the maximum liquid height above the point where the sensor will sit (not the tank height).
- 2Convert to pressure with P = ρ g h, using the density at process temperature.
- 3Add margin (about 10 %) and pick the next standard range.
- 4Choose vented (gauge) cable for open tanks so barometric changes cancel out; keep the vent tube end dry.
- 5Scale the output — convert the 4–20 mA signal with the 4–20 mA calculator.
Our submersible level transmitters are available from 0–5 m to 0–200 m water column; see also the liquid level sensor selection guide and the pressure unit converter.
Frequently Asked Questions
Divide the gauge pressure at the bottom of the liquid by density × gravity: h = P ÷ (ρ × g). For water, 1 bar ≈ 10.2 m and 10 kPa ≈ 1.02 m.
About 9.79 kPa at 20 °C (998 kg/m³), or 9.81 kPa using 1000 kg/m³ — roughly 0.098 bar or 1.42 psi.
Yes. The sensor measures pressure, so a lighter liquid such as diesel shows a higher level for the same pressure. Set the density of the actual liquid, at process temperature, in the transmitter or the controller.
The vent tube in the cable lets the back of the diaphragm see atmospheric pressure, so the transmitter measures gauge pressure and barometric changes do not appear as level changes.
P = 998 × 9.806 65 × 6 ≈ 58.7 kPa ≈ 0.59 bar. With margin, choose a 0–0.6 bar (≈ 0–6 m) or 0–1 bar (≈ 0–10 m) range, depending on how much resolution you need near the top.