Decompression

Bottom Time & Decompression Calculator

Model a single-level dive, its direct ascent, or whole-minute mandatory stops with Bühlmann ZHL-16C and explicit gradient factors.

Plan the square profile

Maximum depth

Bottom time

min

Analyzed oxygen

Ascent rate

m/min

Conservatism

GF low sets the first ceiling anchor; GF high sets the surface limit.

A model output, not a complete dive plan

The calculation assumes instantaneous descent, one constant bottom depth, one O₂/N₂ gas, sea-level pressure, and a constant ascent rate. It does not add an optional safety stop or account for gas supply, oxygen exposure, helium, altitude, workload, previous dives, equipment, or individual susceptibility.

Keep the scenarios separate

This tool starts with rested tissues. Use the repetitive dive model to explore surface-interval tissue carry-over; it intentionally does not create decompression schedules.

Ascent schedule

Profile

Air · 30 m · 35 min

Mandatory decompression stops in descending depth order
Depth	Stop	Runtime out
9 m	3 min	40.3 min
6 m	6 min	46.7 min
3 m	15 min	62.0 min

Modeled NDL: 12 min
Total runtime: 62.3 min
Ascent time: 3.3 min
GF: 40/85

Decompression required

24 min of mandatory stops

Bühlmann ZHL-16C, 40/85, 9 m/min. Mandatory stops are distinct from an optional safety stop.

Total runtime: 62.3 min
Ascent: 3.3 min

Related Guides

Decompression & time limits

Surface Intervals and Repetitive Dives

Understand residual nitrogen between dives, how surface intervals restore no-stop time, and the rules for flying after diving.

Nitrox & oxygen

Equivalent Air Depth (EAD) Explained

Work out the air depth a Nitrox dive is decompression-equivalent to, and see why EAD never changes your oxygen limit.

Decompression & time limits

No-Decompression Limits and Safety Stops

Learn what an NDL represents, compare modelled air and Nitrox limits, and understand how ascent rate and safety stops fit into the plan.

Related Diving Tools

Dive Planning

Repetitive Dive Model

Explore ZHL-16C nitrogen loading across a sequence of square-profile dives and air surface intervals.

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