Eddie Bryant / Below the surface
A little math.
A better understanding.
Scuba tools for the curious, prepared diver. Explore gas, nitrox and buoyancy—with clear results and the assumptions behind them.
Start here / PADI RDP
Interactive Recreational Dive Planner
Click the preview to open the full-screen table, then follow the colored highlights through your selections.
PADI RDP / Imperial
How to use it
- Front: click your depth, then your bottom time. Yellow highlights depth; blue highlights the pressure-group row.
- Surface interval: enter minutes or click a printed interval range. Pink highlights the resulting group.
- Back: click your next depth and pressure-group letter to highlight their intersection.
- Zoom & reset: use + / − to enlarge or reduce the table, and Clear highlights to start over.
Use with your PADI training and the complete table instructions. This reference is for no-decompression air dives; it does not calculate a dive plan.
Open original PDFThe toolkit / Start here
Everyday tools first.
Ordered by likely use in everyday recreational diving, with common preparation tools first and specialized calculations later.
- 01 Nitrox
Nitrox best mix
Calculate the highest oxygen percentage for a planned maximum depth and chosen oxygen partial-pressure limit.
Open calculator - 02 Nitrox
Equivalent air depth
Compare the nitrogen partial pressure of nitrox with air at an equivalent depth.
Open calculator - 03 Nitrox
Maximum operating depth
Find the oxygen partial-pressure depth limit for an analyzed nitrox mix and your selected oxygen limit.
Open calculator - 04 Buoyancy & conditions
Diving weight
Get a rough starting estimate for ballast based on body weight, exposure protection, cylinder, experience and fresh or salt water.
Open calculator - 05 Gas planning
Air consumption
Turn a recorded pressure drop into a surface air consumption (SAC) rate and a cylinder-independent respiratory minute volume (RMV).
Open calculator - 06 Gas planning
Turn pressure
Estimate ascent gas, an additional reserve, and a turnaround pressure using half the gas available above that reserve.
Open calculator - 07 Gas planning
Tank air volume
Estimate the amount of surface-equivalent breathing gas in a scuba cylinder at its current pressure.
Open calculator - 08 Buoyancy & conditions
Altitude correction
Explore how lower surface pressure changes a true water depth's theoretical sea-level equivalent.
Open calculator - 09 Buoyancy & conditions
Lift bag sizing
Estimate an object's submerged weight, the minimum bag displacement, and the surface gas needed to inflate it at depth.
Open calculator - 10 Activity estimates
Diving calories
Estimate energy expenditure for a dive and compare it with an approximate running duration.
Open calculator