Gradient Factors (GF) are two numbers that control how conservative the Bühlmann algorithm is, written as GF Low / GF High. GF High (85) means tissues are allowed to reach 85% of their theoretical M-value limit before the algorithm flags a violation. Lower = more conservative = shorter NDLs. Higher = more aggressive = longer NDLs but less safety margin.

GF Low (40) controls the depth of the first decompression stop if a deco dive occurs. For recreational no-decompression diving, GF Low has minimal impact — GF High drives the NDL.

This planner uses GF 50/85 — Shearwater's current default medium conservatism setting in Rec mode (updated from 40/85 in a 2026 firmware change). This means the planner and your dive computer are working from the same assumptions, making it a true companion for pre-dive planning. (Garmin and Suunto presets may differ — check your own computer's current factory settings.)

This planner will produce NDLs that closely match your Shearwater at factory GF settings. If you have changed your computer to a more aggressive GF, expect the computer to show a longer NDL than this planner.

Never adjust gradient factors to make a profile more aggressive without formal decompression theory training. Increasing GF High toward 95-100 allows tissues to approach their theoretical maximum overpressure — significantly increasing DCS risk. GF 50/85 matches Shearwater's current Rec mode factory default and is the recommended setting for recreational diving.