Every 10 m of seawater adds about one atmosphere of pressure. At the bottom of the Mariana Trench, nearly 11 km down, the pressure exceeds 1,000 atmospheres.
How to use the Water Pressure at Depth Calculator
- Water type
- Depth
- Surface pressure
Results update as you type, every field has its own unit menu, and everything is calculated in your browser.
How it works
Choose fresh or salt water and enter the depth.
Inputs explained
| Field | What to enter |
|---|---|
| Water type | Choose one: Seawater, Fresh water |
| Depth | Units: m, ft, km |
| Surface pressure | Units: kPa, Pa, bar, psi, atm, MPa |
What each result means
- Gauge pressure = [Water type]×9.80665×[Depth]
- Absolute pressure = [Surface pressure] + [Water type]×9.80665×[Depth]
- Atmospheres absolute (ATA) = [Absolute pressure]÷101325
Example values
How the main result changes when Depth changes and everything else stays at the example values above:
| Depth (m) | Absolute pressure (bar) |
|---|---|
| 15 | 2.521 |
| 22.5 | 3.2749 |
| 30 | 4.0288 |
| 37.5 | 4.7827 |
| 45 | 5.5366 |
| 60 | 7.0443 |
Formula
p_gauge = ρ·g·h, p_abs = p_atm + ρ·g·h
Worked example
Inputs — Water type: Seawater; Depth: 30 m; Surface pressure: 101.325 kPa.
Results — Gauge pressure = 3.01554 bar; Absolute pressure = 4.02879 bar; Atmospheres absolute (ATA) = 3.9761 ATA.
Key terms
- Absolute pressure
- Gauge pressure plus atmospheric pressure.
Frequently asked questions
How much does pressure increase per 10 m of seawater?
About 1 bar (1 atm).
What is ATA?
Atmospheres absolute – used by divers for gas calculations.
Why does fresh water give less pressure?
It is about 2.5% less dense.
What is the pressure at the Titanic wreck (3,800 m)?
About 385 bar.