Algorithm — What It Is and Why It Matters
In diving, an algorithm is the mathematical model a dive computer uses to calculate nitrogen (and sometimes helium) absorption and release in your body's tissues during and after a dive. The algorithm determines your no-decompression limits, required decompression stops, ascent ceiling, and safe surface intervals.
The most common algorithms are Bühlmann ZHL-16C (used by Shearwater, Suunto, and many others), RGBM (Reduced Gradient Bubble Model, used by some Mares and Suunto models), and VPM (Varying Permeability Model). Each takes a slightly different approach to modeling bubble formation and dissolved gas behavior, leading to different levels of conservatism.
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Frequently Asked Questions
Which dive computer algorithm is the safest?
No single algorithm is universally safest — each models decompression differently. What matters most is using your computer's conservatism settings appropriately for your fitness, age, hydration, and dive conditions. A more conservative algorithm setting on any model adds safety margin.
Can I change the algorithm on my dive computer?
Most dive computers use a fixed algorithm but allow you to adjust conservatism settings within it. A few high-end models, like Shearwater computers, let you switch between Bühlmann and VPM-B algorithms.
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