Calculator Inputs
Enter the deepest planned depth, actual bottom time, breathing gas, previous pressure group, and surface interval. The calculator rounds depth upward and estimates no-stop loading with conservative adjustments.
Example Data Table
These examples show common educational inputs. They are not dive permissions.
| Profile | Depth | Bottom Time | Gas | Previous Group | Surface Interval | Use Case |
|---|---|---|---|---|---|---|
| Shallow reef | 40 ft | 45 min | Air | None | 0 min | First dive estimate |
| Training wall | 60 ft | 35 min | Air | None | 0 min | Single dive planning |
| Second reef | 70 ft | 25 min | Air | F | 80 min | Repetitive dive check |
| Nitrox practice | 80 ft | 22 min | 32% | C | 120 min | EAD and ppO2 review |
Formula Used
Equivalent Air Depth:
EAD = ((Depth + 33) × (1 - FO2) / 0.79) - 33
Residual Nitrogen Time:
RNT = ceil((Residual Group Index / 14) × (NDL × 0.50))
Adjusted Table Time:
Adjusted Time = ceil((Bottom Time + RNT) × Conservative Factor)
Available Bottom Time:
Available Time = NDL - RNT
Oxygen Partial Pressure:
ppO2 = FO2 × ((Depth + 33) / 33)
The calculator rounds equivalent air depth upward to the next table depth. Pressure groups are estimated with proportional bands. This is not an official table replacement.
How to Use This Calculator
- Enter the deepest point of the planned dive.
- Choose feet or meters before calculating.
- Enter actual bottom time in minutes.
- Use 21 for air, or enter the planned nitrox oxygen percentage.
- Select the previous pressure group for repetitive planning.
- Enter the surface interval after the earlier dive.
- Add a safety stop and conservative margin.
- Press the calculate button.
- Review no-stop status, residual time, pressure group, ppO2, and warnings.
- Export the result as CSV or PDF for records.
Educational Guide to Dive Table Planning
Why Dive Tables Matter
Dive tables help divers think before entering the water. They connect depth, time, and surface intervals. A deeper dive usually gives less no-stop time. A long dive also increases nitrogen loading. Repetitive dives add another layer. The body may still hold residual nitrogen from the earlier dive. That remaining load can reduce the safe time for the next profile.
What This Calculator Estimates
This page estimates table depth, available time, residual nitrogen time, and an ending pressure group. It also checks oxygen exposure when nitrox is selected. The equivalent air depth method is useful for nitrogen planning. It converts a nitrox dive into an air-depth estimate. The tool then rounds that depth upward. Rounding upward gives a more conservative table value.
Using Conservative Inputs
Real dives are rarely perfect square profiles. Divers may work hard, become cold, or descend deeper than planned. For that reason, this calculator includes a conservatism field. It increases the adjusted table time. That makes the result stricter. It is wise to plan shorter dives than the maximum estimate.
Repetitive Dive Thinking
Repetitive planning starts with the ending pressure group from the earlier dive. A surface interval lowers the estimated residual group. The calculator then converts the remaining group into residual nitrogen time. That time is added to the next bottom time. The combined number is compared with the selected no-stop limit.
Important Safety Limits
This calculator is only an educational aid. It does not replace official tables, dive computers, current course materials, or professional instruction. Always plan with a buddy. Check gas supply, weather, current, equipment, temperature, and emergency procedures. Never use an online calculator as the final authority for a real dive.
FAQs
1. Is this an official NAUI dive table?
No. This is an educational calculator inspired by table-style planning. Use official materials, instructor guidance, and a reliable dive computer for real dives.
2. What is equivalent air depth?
Equivalent air depth estimates the air depth that gives similar nitrogen exposure when using nitrox. It helps compare nitrox dives against air-based planning limits.
3. What is residual nitrogen time?
Residual nitrogen time estimates leftover nitrogen from a previous dive. It is added to the next dive time to create a more conservative planning value.
4. Why does the calculator round depth upward?
Tables normally use listed depth rows. If a dive falls between rows, using the deeper row is more conservative and reduces planning risk.
5. Can I use this for decompression diving?
No. This calculator is for educational no-stop planning only. Decompression dives require advanced training, proper software, redundancy, and expert procedures.
6. Why is ppO2 shown?
Oxygen partial pressure matters when nitrox is used. A higher oxygen percentage can reduce nitrogen load but increases oxygen exposure risk at depth.
7. What does conservatism do?
Conservatism increases the adjusted table time. This makes the estimate stricter and encourages shorter dives with more remaining margin.
8. Should I still make a safety stop?
Follow your training and local procedures. A safety stop is commonly used on recreational dives, especially after deeper or longer profiles.