Dive Calculator

Recreational dive calculator

by Nikolay Kunev · an independent calculator based on the PADI^® Recreational Dive Planner

Imperial units
RDP — EANx (Nitrox)

How does the calculator work?

Choose a modePADI RDP for recreational no-decompression dives (up to 40m / 130ft). BG Tables — for dives requiring decompression stops. Nitrox — for enriched air dives (EANx 22–40% O₂): you also enter the oxygen percentage and the calculator adds pO₂, MOD, EAD and oxygen exposure.
Choose unitsMetric or imperial. Switch any time.
Enter the first diveMaximum depth and bottom time (ABT — Actual Bottom Time).
Read the resultPressure Group (A–Z) and NDL for PADI; for BG mode — residual nitrogen index and mandatory decompression stops.
Add a repetitive divePress "+ Add next dive" → enter the surface interval (hours and minutes) → enter the next dive's depth and time. Or in reverse — if you want to know how much surface time you'll need for a desired dive, enter the dive's parameters first without filling in the surface interval.
Reverse planningFor every repetitive dive, the calculator shows the minimum required surface interval — how long you need to wait between dives to make the next one safely.
If you see a red warningIf your next dive exceeds the limits (red ABT/NDL warning), look up at the "Surface interval" section above that dive. The calculator already shows the minimum required interval there — press the "Apply" button to fill it in automatically. The warning will clear.

⚠ The calculator rounds depth and time up to the next table value for added safety. Always check the warnings before a real dive, and stay within your training.

Nitrox (EANx) — for certified Enriched Air divers only

This mode plans dives on enriched air (22–40% O₂). The nitrogen side is computed via Equivalent Air Depth (EAD) against the air RDP table; the oxygen side via partial pressure and the NOAA exposure limits. This is the procedure PADI describes for using the RDP with enriched air; results are equal to or more conservative than the dedicated EANx tables.

pO₂ maximum 1.4 ata — that is 111 ft on EANx 32 and 95 ft on EANx 36. Between 1.4 and 1.6 ata is for contingency planning only; above 1.6 — never.
Track your oxygen exposure — allowable time is the shorter of the NDL and the remaining time by O₂. Never exceed 100% in 24 hours (90% recommended); after 100%, wait 12 hours. Keep at least 1 hour on the surface between enriched air dives.
Analyse your own mix before every dive and label the cylinder. The calculation is only valid for the percentage you enter.
Safety stop and repetitive-dive rules are the same as for the air RDP (based on actual depth).
The calculator rounds both depth and EAD up to the next table row — as in the PADI procedure.

How is it computed?

Oxygen partial pressure (Dalton's law): pO₂ = FO₂ × (D/33 + 1) in ata, D in feet (metric: D/10 + 1).

Maximum operating depth: MOD = (1.4 / FO₂ − 1) × 33 ft; contingency ceiling at 1.6 ata.

Equivalent air depth: EAD = (D + 33) × (1 − FO₂) / 0.79 − 33. The depth at which air would give the same nitrogen loading. Following the PADI procedure, the actual depth is first rounded up to a table row, then the EAD is rounded up to a column, from which NDL, pressure group, residual nitrogen and surface interval are read. Metric units use the metric RDP table, imperial units the imperial one.

Oxygen exposure (DSAT method): the NOAA limit for the pO₂ (e.g. 1.4 ata → 150 min, 1.1 ata → 240 min, 1.6 ata → 45 min) is 100% of the allowable exposure for 24 hours. Each dive uses time / limit, rounded up to 5%; the percentages add up over the day. pO₂ is rounded up to the next 0.1 step; pO₂ ≤ 0.5 does not count.

Recommended mix: the richest mix that keeps pO₂ ≤ 1.4 at the planned depth: FO₂ = 1.4 / (D/33 + 1), rounded down to a whole percent.

The formulas are in the public domain (NOAA Diving Manual, diving physics textbooks). No data from the PADI EANx tables is used.

Flying after diving recommendation