Pressure & Depth Converter
Instant conversions: bar ↔ psi, metres ↔ feet, absolute pressure ↔ depth, fresh vs salt water.
Depth
Pressure
Temperature
Calculation model
Simplified mode: P_atm rounded to 1 bar and simplified sea water density. Sufficient for recreational diving (error < 1% at 30 m).
Glossary
7 termes essentiels
Frequently asked questions
6 questions
At 30 m in sea water, absolute pressure is approximately 4.013 bar (≈ 58.2 psi). In simplified mode, you get 4.000 bar — the difference is less than 1%.
Salt water has a density of approximately 1025 kg/m³ versus 1000 kg/m³ for fresh water. At the same depth, the salt water column is heavier and therefore exerts more pressure.
Multiply the bar value by 14.5038. Example: 200 bar × 14.5038 = 2,900.8 psi. Quick rule: psi ÷ 15 ≈ bar.
Gauge (or relative) pressure is the pressure exerted by the water column alone, without accounting for atmospheric pressure. At 10 m, it is approximately 1 bar.
Yes. The difference between the simplified model (P_atm = 1 bar, divisor 10) and the real sea water model is less than 1% down to 40 m. Most dive tables use this approximation.
Above the thermocline (∼15 m), temperature drops slowly (≈ 0.1 °C/m). Below, the drop accelerates (≈ 0.3 °C/m). The physiological minimum is around 4 °C at depth.
How to calculate absolute pressure when diving?
Absolute pressure in diving is calculated by adding atmospheric pressure to hydrostatic pressure. Simplified: P_abs = depth ÷ 10 + 1 bar. Sea water: P_abs = depth ÷ 10 + 1.013 bar. Fresh water: P_abs = depth ÷ 10.3 + 1.013 bar. At 30 m in sea water, you get 4.013 bar or approximately 58.2 psi.
What is the difference between absolute and gauge pressure?
Absolute pressure includes atmospheric pressure (≈ 1.013 bar at sea level) plus the water column pressure. Gauge pressure only measures the pressure exerted by the water. For a diver at 20 m in sea water: P_abs ≈ 3.013 bar, P_gauge ≈ 2.000 bar.
Why does pressure vary between fresh and salt water?
Salt water density (≈ 1025 kg/m³) is higher than fresh water (1000 kg/m³). This means that at the same depth, pressure is slightly higher in salt water. At 10 m: salt water ≈ 2.019 bar, fresh water ≈ 1.984 bar.
How to convert bar to psi and back?
The exact conversion is 1 bar = 14.5038 psi. To convert bar to psi, multiply by 14.5038. For the reverse, divide by 14.5038 (or multiply by 0.0689476). Mnemonic tip: psi ÷ 15 ≈ bar, handy on the boat.