ATA Calculator (Atmospheres Absolute)
Use this tool to convert depth ↔ ATA for scuba diving and hyperbaric planning.
What is ATA?
ATA means Atmospheres Absolute. It describes total pressure on a diver, including atmospheric pressure at the surface plus water pressure at depth. At sea level on the surface, pressure is about 1 ATA. As you descend, pressure increases.
ATA matters in scuba diving, technical diving, and hyperbaric oxygen therapy because pressure changes affect gas density, gas absorption, decompression stress, and oxygen exposure limits.
ATA Formula
The calculator uses standard recreational approximations:
- Salt water: Constant ≈ 33 ft or 10 m
- Fresh water: Constant ≈ 34 ft or 10.4 m
To reverse the formula:
How to Use This ATA Calculator
1) Convert Depth to ATA
- Select Depth to ATA.
- Enter your depth.
- Choose feet or meters and the water type.
- Click Calculate.
2) Convert ATA to Depth
- Select ATA to Depth.
- Enter a target ATA (must be 1.0 or higher).
- Choose output unit and water type.
- Click Calculate to get depth.
Quick Reference Table (Salt Water)
| Depth (ft) | Approx ATA | Pressure (psi) |
|---|---|---|
| 0 | 1.00 | 14.70 |
| 33 | 2.00 | 29.39 |
| 66 | 3.00 | 44.09 |
| 99 | 4.00 | 58.78 |
| 132 | 5.00 | 73.48 |
Why ATA is Important in Diving
Gas Consumption
At higher ATA, each breath contains more gas molecules. Your tank empties faster as depth increases, even if your breathing rate feels the same.
Nitrogen Absorption
Increased pressure raises nitrogen partial pressure, which can increase narcosis risk and decompression obligations, especially on longer or deeper dives.
Oxygen Exposure
ATA directly affects oxygen partial pressure (PO2). This is critical for nitrox and technical gas planning to remain within safe PO2 limits.
Common ATA Questions
Is 10 meters always exactly 2 ATA?
Not exactly in all water types and conditions, but it is a widely accepted approximation in salt water for practical planning.
Does altitude change ATA calculations?
Yes. Surface pressure is lower at altitude, so true calculations shift. Use altitude-adjusted dive procedures when relevant.
Can I use this calculator for dive certification planning?
Use it as a learning aid. For actual dives, rely on trained instruction, dive tables, certified software, and your dive computer.