CNS Oxygen Clock Calculator
Estimate CNS oxygen exposure over multiple constant-depth Nitrox dives and account for recovery during surface intervals.
Track your oxygen clock.
Add dives in order. Each dive contributes CNS exposure from ppO₂ and time; surface intervals reduce retained CNS before the next dive.
How cumulative CNS oxygen exposure is estimated
CNS exposure is estimated from oxygen partial pressure and exposure time. Each dive contributes a percentage of the planning limit for its ppO2, while surface intervals reduce the retained CNS value before the next exposure.
Example: an exposure at ppO2 1.4 bar uses the applicable exposure-time limit for that ppO2. A shorter exposure consumes only part of the 100% planning clock, and the retained value is reduced during the following surface interval.
CNS calculations are planning references, not predictions of individual susceptibility to oxygen toxicity. Use conservative limits, analysed gas and the oxygen-exposure procedures taught by your training agency.
The calculator updates instantly from the values you enter and shows the core planning result in the dark result card.
Use realistic values from your own diving and leave a practical margin for changes in workload, conditions and equipment.
Treat this page as an educational reference and cross-check the result with your training, analysed gas and an appropriate dive-planning method.