Dive Table Calculator
Look up no-decompression limits and pressure groups using the Recreational Dive Planner (RDP). Plan repetitive dives with surface interval adjustments and residual nitrogen tracking.
1First Dive
Dive 1 Inputs
RDP covers 10 - 40m. Max recreational depth: 40m.
Time from descent to start of ascent.
Your depth of 18m maps to the 18m row in the RDP (always round up to the next table depth).
Dive 1 Results
Surface Interval
Surface Interval Input
Minimum recommended: 60 min between recreational dives.
Each 30 minutes of surface interval moves you one pressure group letter lower. After 180 minutes you return to group A (fully off-gassed for RDP purposes).
After Surface Interval
2Second Dive
Dive 2 Inputs
Repetitive dives should be shallower than the first dive where possible.
14m maps to the 14m RDP row.
Dive 2 Results
What are dive tables?
Dive tables are mathematical tools developed to help recreational divers plan dives that avoid decompression sickness (DCS). The first decompression tables were published by the Royal Navy in 1908, based on J.B.S. Haldane's research into how nitrogen dissolves and comes out of solution in body tissues under pressure.
The PADI Recreational Dive Planner (RDP), introduced in 1988, was specifically designed for no-decompression recreational diving. Unlike military tables, the RDP uses a multi-tissue model and builds in conservative safety margins to reduce DCS risk for divers at all experience levels.
How to read the RDP
The RDP consists of three tables. Table 1 (used here) shows the no-decompression limit (NDL) for each depth and assigns a pressure group letter (A through N) based on your bottom time. The further into the alphabet, the more nitrogen you are carrying.
To use Table 1: find the column for your depth (or the next deeper depth if yours isn't listed), then read down to find the row where your bottom time first appears. The pressure group letter in that cell is your group at the end of the dive.
Always round your depth up to the next table depth - never interpolate down. Similarly, round your bottom time up to the next minute if it falls between entries.
Repetitive dive planning
After a dive, nitrogen remains dissolved in your tissues. This residual nitrogen reduces your no-decompression time on subsequent dives. The RDP accounts for this through pressure groups and a surface interval credit.
Table 2 of the physical RDP card tracks how your pressure group decreases over a surface interval. Table 3 then shows your Residual Nitrogen Time (RNT) - the number of minutes you must add to your actual bottom time when looking up your new pressure group on Table 1. This tool uses a simplified version of this process for quick planning estimates.
Key rules for repetitive dives: always plan the deepest dive first, use the full surface interval credit before diving again, and be more conservative with multiple dives in a day (three or more dives significantly increases DCS risk).
Tables vs dive computers
Modern dive computers track multi-tissue nitrogen loading continuously throughout a dive, giving a more accurate and often more permissive NDL than static tables. However, tables remain essential for several reasons:
- Backup planning: If your computer fails mid-dive, you need to know how to surface safely.
- Pre-dive planning: Tables help you confirm your dive plan before you enter the water.
- Education: Understanding tables builds the conceptual knowledge needed to use a computer correctly.
- Certification requirement: All major agencies (PADI, SSI, BSAC) require divers to demonstrate table proficiency.
Never plan your dive solely on a calculator or app - always cross-reference with your actual dive computer in the water and follow the more conservative of the two limits.