Gradient Factor — What It Is and Why It Matters
Gradient factors (GF) are a pair of percentages that control how conservatively a Bühlmann algorithm manages decompression. Expressed as GF Low/High (e.g., GF 30/70), the low value governs the depth of the first (deepest) decompression stop, and the high value sets the surfacing criterion — how much nitrogen can remain in your tissues when you reach the surface.
Lower gradient factor numbers mean more conservative profiles (longer deco, deeper first stops). A GF of 100/100 represents the raw Bühlmann M-values with no added conservatism. Common recreational settings range from GF 30/70 to GF 40/85. Understanding and adjusting gradient factors gives technical divers fine-grained control over their decompression profiles.
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Frequently Asked Questions
What gradient factors should a recreational diver use?
Most recreational divers never need to adjust gradient factors — the default settings on their dive computer are appropriate. If your computer does expose GF settings, GF 40/85 or GF 30/80 are common recommendations. Consult a qualified instructor before changing these values.
What does GF Low control vs GF High?
GF Low controls the depth of the first mandatory decompression stop on a deco dive. GF High controls the tissue saturation percentage allowed at the surface. Together, they create a linear interpolation between the deepest stop and surfacing, determining all intermediate stop depths and times.
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