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.
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 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. There's no paywall, no account, and it keeps working with no signal.
⚠ 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.