Is DecoLog's decompression planner free?

Yes — it's free forever, with no signup, no subscription and no ads. It runs in your browser and works offline once loaded.

Which decompression algorithms does it use?

Bühlmann ZHL-16C with gradient factors, and VPM-B with conservatism levels +0 to +5 — the two models technical divers rely on.

Does it support trimix and CCR?

Yes. It plans trimix (helium) dives, multi-gas open-circuit deco, and closed-circuit rebreather dives including an open-circuit bailout schedule.

Can I trust the numbers?

The engine is validated against reference dive software, but every model is an approximation. Always dive a functioning computer and verify any plan independently.

{ DECO PLANNER }

Free decompression planner — ZHL-16C & VPM-B

Plan your decompression before you get wet. DecoLog runs the two algorithms technical divers actually use — Bühlmann ZHL-16C with gradient factors and VPM-B — and returns a stop-by-stop schedule with runtime, gas switches and time-to-surface. It's free and runs in your browser.

What a decompression planner does

Past your no-decompression limit you can no longer ascend straight to the surface. A planner models how nitrogen and helium load into and out of 16 tissue compartments at depth, then tells you how long to pause at each stop so you off-gas within safe limits. DecoLog shows the first stop, every stop depth and time, the gas breathed at each, and the total runtime.

Bühlmann ZHL-16C with gradient factors

ZHL-16C is the dissolved-gas model inside most dive computers. Gradient factors (a GF-low / GF-high pair such as 30/85) let you dial conservatism: a lower GF-low introduces deeper stops, while a lower GF-high adds shallow-stop time. DecoLog lets you set both and see the schedule update instantly — our gradient-factors guide explains exactly what the two numbers do.

VPM-B — the bubble model

VPM-B takes a different approach: it limits how large gas micro-bubbles are allowed to grow. In practice it places deeper first stops than a pure Bühlmann profile. DecoLog implements VPM-B with conservatism levels +0 (least) to +5 (most), so you can compare it directly against your gradient-factor plan.

Trimix, CCR and multi-gas

Add helium to cut narcosis and breathing-gas density; the planner tracks equivalent narcotic depth, accumulates your CNS clock and OTUs across the dive, and switches you to richer decompression gases (EAN50, oxygen) at the depths where they're safe. Rebreather divers get loop and diluent planning at a fixed setpoint, plus an open-circuit bailout schedule in case the unit fails.

Validated — and free

DecoLog's deco math is checked against reference dive software: its ZHL-16C no-stop limits and a published VPM-B reference profile reproduce to within a couple of minutes — the full trust story is on how we validate. There's no paywall, no account, and it keeps working with no signal.

Try it now — free, in your browser. • OPEN THE PLANNER

⚠ DecoLog is a planning aid, not a substitute for a dive computer or proper training. Decompression, trimix and rebreather diving require certification. Verify every plan independently and dive within your limits.