Plan a Recreational Dive
This calculator uses a simplified no-decompression table model for educational planning. Always cross-check with your certified training agency tables/computer and local dive procedures.
How this dive table calculator works
A dive table calculator helps estimate whether your planned depth and bottom time fit within no-decompression limits (NDL). Staying within NDL means you can make a direct ascent (with a safety stop) without mandatory decompression stops. This page uses a practical, conservative model based on common recreational table values from 35 to 130 feet.
The calculator does three main things:
- Rounds your planned depth up to the next deeper standard table depth.
- Finds the corresponding no-decompression limit for that depth.
- Checks your planned (or adjusted repetitive) bottom time against that limit.
Quick reference: simplified no-decompression limits
| Depth (ft) | NDL (min) |
|---|---|
| 35 | 205 |
| 40 | 140 |
| 50 | 80 |
| 60 | 55 |
| 70 | 45 |
| 80 | 35 |
| 90 | 25 |
| 100 | 20 |
| 110 | 16 |
| 120 | 13 |
| 130 | 10 |
Why depth rounding matters
Dive tables are designed in fixed depth increments. If you plan a dive to 72 feet, the table depth used should be 80 feet, not 70. Rounding up adds conservatism and better reflects the risks of nitrogen absorption as depth increases.
Repetitive dive planning basics
If you are doing a second dive, your body may still hold residual nitrogen. This calculator accepts optional previous-dive inputs and estimates a residual nitrogen time penalty. That penalty is added to your planned bottom time on the next dive to produce an adjusted bottom time.
Inputs used for repetitive planning
- Previous depth/time: used to estimate initial nitrogen load.
- Surface interval: used to estimate off-gassing before the next dive.
- Current planned depth: determines how strict the next NDL is.
Even if your adjusted time looks acceptable, remain conservative. Conditions like cold water, exertion, poor visibility, and stress can increase risk.
Safe ascent reminders
- Ascend at 30 ft/min or slower.
- Perform a safety stop of 3-5 minutes at 15-20 feet for most dives deeper than 30 feet.
- Maintain good buoyancy and avoid rapid depth changes near the surface.
- Hydrate, rest, and extend surface intervals when possible.
Important limitations
This tool is educational and not a replacement for formal training, agency-approved tables, local dive briefings, or your dive computer. It does not account for altitude diving, gas mix changes (nitrox/trimix), decompression diving protocols, emergency contingencies, or individual medical factors.
For real-world dive operations, use standardized planning workflows, buddy checks, and instructor/divemaster guidance.