Dive Inputs
Depth and Time Chart
Example Data Table
| Depth | Time | Surface Interval | Second Depth | Result |
|---|---|---|---|---|
| 18 m | 35 min | 60 min | 14 m | Practice plan allowed |
| 25 m | 28 min | 45 min | 18 m | Review required |
| 30 m | 22 min | 30 min | 16 m | Limit warning |
Formula Used
NDL: selected from an educational depth table.
Pressure ratio: bottom time ÷ no-decompression limit.
Residual nitrogen: group index × 2.5 × e-surface interval ÷ 180.
Total nitrogen time: second bottom time + residual nitrogen time.
Adjusted limit: second no-decompression limit - residual nitrogen time.
How to Use This Calculator
Enter the planned depth and bottom time for the first dive. Add your surface interval. Then enter the second dive depth and time. Press calculate. The tool estimates an educational pressure group, residual nitrogen time, adjusted limit, and final status. Use the chart to compare depth and time quickly.
Educational Article
Understanding Dive Table Math
Dive table planning uses depth, time, and surface recovery. The goal is simple. A diver wants to estimate nitrogen loading before another dive. Deeper dives usually reduce allowed bottom time. Longer dives increase nitrogen exposure. Surface intervals reduce some stored nitrogen.
Why Pressure Groups Matter
A pressure group is a letter style score. It describes estimated nitrogen after a dive. A low letter means less loading. A high letter means more loading. In real training, official tables use tested values. This calculator uses simplified educational logic.
Surface Interval Effect
Time on the surface matters. Nitrogen leaves the body gradually. A longer break lowers residual nitrogen. That can increase the adjusted limit for the next dive. Short breaks leave more nitrogen. That makes repetitive dives more restricted.
Repeated Dive Planning
For a second dive, residual nitrogen is added to planned bottom time. This creates total nitrogen time. The total is compared with the limit for the second depth. If total nitrogen time is too high, the plan needs changes. The diver may reduce depth, reduce time, or extend the surface interval.
Safe Learning Use
This page supports math practice only. It should not guide real dives. Diving requires certified training, current tables, computers, local rules, and professional judgment. Always follow your instructor, agency materials, and dive computer.
FAQs
Is this an official PADI calculator?
No. It is an educational planning simulator. Use official training materials for real dives.
Can I use this for actual diving?
No. Real diving needs certified instruction, official tables, and a dive computer.
What is bottom time?
Bottom time is the planned time spent underwater at the selected depth.
What is residual nitrogen?
Residual nitrogen is estimated nitrogen left after a previous dive and surface interval.
Why does deeper depth reduce time?
Greater depth increases pressure. This usually increases nitrogen absorption faster.
What is a pressure group?
It is a letter category showing estimated nitrogen loading after a dive.
Why add a safety stop?
A safety stop adds conservative practice before surfacing from many dives.
Why include downloads?
Downloads help save practice results for learning, review, and comparison.