Minimum Gas & Rock Bottom Calculator
Estimate minimum gas and rock-bottom turn pressure for a shared-gas ascent that includes problem solving, ascent and a 5 m safety stop.
Know your minimum gas.
Set maximum depth, SAC per diver, cylinder size, number of divers sharing gas and the reserve you want remaining at the surface.
What minimum gas / rock bottom represents
Minimum gas estimates the amount needed to deal with a gas-sharing emergency at the maximum planned depth and ascend while both divers breathe from the same supply. The model includes problem-solving time, ascent gas, a safety stop and the reserve selected for reaching the surface.
Example: at 30 m, two divers sharing gas consume substantially more than one diver because both SAC rates are exposed to the ambient pressure. The required gas is converted back into cylinder pressure so you can see the approximate pressure at which the ascent must begin.
Minimum gas depends heavily on SAC, team size, cylinder volume, ascent assumptions and the chosen reserve. Use values and procedures from your training. This calculator is an educational planning aid, not a replacement for team gas planning.
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.