multiple dive plan
A dive plan for several days that stays inside the no-decompression limits.
Enter the trip name, the start and end dates, the group size, and each day's site. The number of days follows those dates. Each dive has its own mix and cylinder, and a rest day still counts toward residual nitrogen.
Gas includes an 18 m/min descent, bottom time, a 9 m/min ascent, and a 5-minute safety stop at 5 m when the dive is deeper than 9 m. Each dive starts again from its own start pressure. The surface interval runs from the next dive's start time, after the diver is back on the surface.
CNS and OTU cover the descent, bottom, ascent, and safety stop at each segment's PPO2. The CNS clock halves every 90 minutes on the surface. OTU adds up across the trip, with no credit during the surface interval. On the nitrogen table, exactly 12 hours usually leaves group A. More than 12 hours clears it.
RG is the group letter. RT is residual nitrogen. BT is bottom time. TT is RT plus BT. On the next dive, BT is the minutes you still have, and TT is RT plus BT. SI is the surface interval. D is depth. A safety stop of 3–5 minutes at 5 m is recommended deeper than 9 m.
What the words mean
- Group
- A letter for the nitrogen you still carry. A is the least. Later letters mean more nitrogen.
- Residual nitrogen
- Nitrogen still stored in your body after the dive you just did. The table writes that leftover as minutes already spent at the next dive's depth.
- Bottom time
- How long you stay at the dive depth, in minutes.
- Surface interval
- How long you stay on the surface between two dives. Nitrogen leaves during this rest.
- PPO2
- PPO2 stands for partial pressure of oxygen. It is how hard the oxygen presses on you at that depth. The number rises as you go deeper.
- MOD
- MOD stands for maximum operating depth. It is the deepest you can go on this mix before the oxygen passes the limit you set.
- EAD
- EAD stands for equivalent air depth. Nitrox has less nitrogen than air, so the dive is counted as shallower than the depth you actually are.
- Gas
- An estimate of the litres one diver uses. It comes from the SAC rate and the pressure, for an 18 m/min descent, the bottom time, a 9 m/min ascent, and a 5-minute safety stop at 5 m when the dive is deeper than 9 m.
- Reserve
- The lowest pressure that should still be in the cylinder when you are back on the surface. If the calculated end pressure is under this number, the plan is marked as a risk.
- SAC
- SAC stands for Surface Air Consumption, the gas you use per minute at the surface, in litres. At depth, that rate is multiplied by the pressure.
- CNS
- CNS is the oxygen clock for the nervous system. In this plan it covers the descent, the bottom, the ascent, and the safety stop, then halves every 90 minutes on the surface.
- OTU
- OTU stands for oxygen toxicity unit, the oxygen dose for the lungs. In this plan the dose adds up across the trip, with no credit during the surface interval.
Calculations in this tool follow the U.S. Navy Air Tables, the NOAA Oxygen Exposure Limits, and the OTU rate table. This tool is only a dive planning aid. It is not a substitute for formal training, certification, or the judgment of a dive computer or a guide on site. The decision to dive, and safety underwater, remain each diver's own responsibility. Always plan your dive and dive your plan.