SAC & RMV
Feed it one real dive — pressures, cylinder, time, average depth — and get your RMV and SAC. Save it, and your personal average follows you into the gas planner.
Your RMV learns — save a few real dives and the gas planner will use your personal average automatically.
The maths, explained
Your RMV — respiratory minute volume — is the number worth remembering: the litres of gas you breathe per minute, referenced to the surface, independent of any cylinder. From a real dive:
RMV = (bar used × cylinder litres) ÷ (minutes × P) where P = average depth ÷ 10 + 1
SAC in bar/min is the same measurement left on one cylinder — useful at the gauge, meaningless on any other cylinder. That is why the planner stores RMV, not SAC.
Measure it over several relaxed dives, not one working dive, and let the average settle. Then plan with honesty: a stressed diver breathes far more than a resting one, which is exactly why the gas planner keeps a third of your gas untouchable.
This Is Exactly What We Teach On Intro to Technical Diving
Knowing your consumption is the first habit of a technical diver. Intro to Technical Diving builds the trim, finning and gas awareness that bring that number down for good.
Checked, not trusted: the formulas on this page are pinned by 130 automated reference checks that run on every change — cross-validated against Subsurface’s published planner tests, the independent DecoTengu implementation, printed MOD tables and the team’s own Splash apps.
For training and planning purposes only. Analyse every mix before you breathe it and always dive within your certification.