Depth & Pressure
Calculator
Convert depth units and calculate pressure, lung compression, and narcosis thresholds for any freediving target depth.
Target Depth
Lung Volume Parameters
Average adult: TLC 6.0 L, RV 1.5 L. Adjust for your physiology.
Results at 20 m
Depth Conversions
Absolute Pressure
Lung Volume at Depth (Boyle's Law)
Moderate — breathe fully before diving
Always dive with a trained buddy. Lung squeeze requires medical attention.
Depth Reference Table
| Depth (m) | Pressure (ATM) | Lung Volume | Notes |
|---|---|---|---|
| 0 m | 1 ATM | 6 L (100%) | Surface — full breath |
| 10 m | 2 ATM | 3 L (50%) | AIDA 2★ minimum |
| 16 m | 2.6 ATM | 2.31 L (39%) | AIDA 2★ cert requirement |
| 20 m | 3 ATM | 2 L (33%) | AIDA 2★ recreational max |
| 24 m | 3.4 ATM | 1.76 L (29%) | AIDA 3★ cert requirement |
| 30 m | 4 ATM | 1.5 L (25%) | Blood shift activates |
| 40 m | 5 ATM | 1.2 L (20%) | AIDA 4★ recreational max |
Depth & Pressure — Key Concepts
How does pressure increase with depth in freediving?expand_more
Pressure increases by 1 bar (1 ATM) for every 10 metres of depth in seawater. At the surface you experience 1 ATM. At 10m the pressure is 2 ATM, at 20m it is 3 ATM, and so on. This means your lungs compress to half their surface volume at 10m.
What is lung squeeze in freediving?expand_more
Lung squeeze (thoracic squeeze) occurs when a freediver descends beyond the depth where their total lung volume compresses below residual volume — the minimum lung volume the body can sustain. At depths below approximately 30–40m, blood shift compensates, but if a diver descends too fast or lacks adequate breathwork, tissue damage in the lungs can occur.
How deep can a beginner freediver safely go?expand_more
An AIDA 2 certification covers dives to approximately 20m with a trained buddy. Most recreational freedivers dive to 10–20m. Deeper dives (30m+) require advanced training, equalization technique, and an experienced dive partner.