Decompression planner
Stops, depths and total ascent time for a planned profile, on Buhlmann ZH-L16C with the gradient factors you choose.
Free to use, no account needed. The calculator loads below.
Read this before you read the numbers
Decompression diving is a trained discipline, not a calculator output. This planner exists to let a trained diver check a profile and understand how the model responds to a change, not to qualify anybody to run one. If a plan here is the only reason you would do a dive, that is the reason not to.
Nothing on this page accounts for your gas supply, your team, your exit, the conditions, your thermal status or your workload, and every one of those things has ended decompression dives that the numbers said were fine.
What gradient factors do
Buhlmann gives each tissue compartment a supersaturation ceiling, the M-value. Gradient factors express your stops as a percentage of that ceiling: the low factor sets how close you come at the deepest stop, and the high factor sets how close you are as you surface.
A common conservative setting is 30/70. A looser one is 50/85. Lowering the low factor brings your first stop deeper and lengthens the dive; lowering the high factor keeps you shallower for longer at the end. Both directions trade time in the water for margin.
Total ascent time is the number to plan around
The individual stops matter less than what they add up to. A profile that gains three minutes of bottom time and twenty minutes of ascent has not gained you anything, and it has changed your gas requirement, your thermal exposure and your surface support window.
Plan the ascent as part of the dive, not as the thing that happens afterwards, and carry the gas for it with the reserve untouched.
Common questions
What are gradient factors in decompression diving?
They set how close to the Buhlmann model's supersaturation ceiling you are willing to come, as a pair of percentages. The first applies at the deepest stop, the second at the surface. Lower numbers are more conservative and mean longer ascents.
What gradient factors should I use?
That is a question for your training and your own risk tolerance, not for a web page. 30/70 and 40/85 are both in common use. Whatever you choose, use it consistently and understand what changing it does before you change it.
Can I use this instead of desktop planning software?
No. This is a planning aid for checking a profile and seeing how the model responds. Real decompression diving is planned with redundancy, gas planning, contingency profiles and a team, and it is taught rather than downloaded.
Is this the same model as my dive computer?
It is Buhlmann ZH-L16C with gradient factors, which is what most technical computers run. Your computer's exact implementation, compartment handling and default conservatism may still differ, so never treat the two as interchangeable.
The rest of it lives in the app
The app plans multi-gas profiles with switches, tracks the ascent live on your wrist, and logs the profile you actually dived against the one you planned.