⚠️ Educational tool — not dive-planning software
This page is for learning and rough estimates only. Always follow your training, your dive tables, and your dive computer — they account for factors a web page cannot. Never plan a real dive from a website.
Your surface air consumption
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How it's calculated
In metric, the formula is:
SAC = (start bar − end bar) × tank litres ÷ minutes ÷ (depth ÷ 10 + 1)
The first part converts the pressure you used into litres of gas. Dividing by dive time gives
litres per minute at depth. Dividing by (depth ÷ 10 + 1) — the absolute pressure
in atmospheres, since every 10 m of seawater adds one atmosphere — normalizes it to the
surface.
In imperial, tank pressure alone does not tell you the gas volume, so the tank's rated pressure enters the formula:
RMV = ((start psi − end psi) ÷ rated psi) × tank cu ft ÷ minutes ÷ (depth ÷ 33 + 1)
Here every 33 ft of seawater adds one atmosphere. The result is often called RMV (respiratory minute volume) and is expressed in cubic feet per minute.
Typical relaxed divers land somewhere around 15–20 L/min (0.5–0.7 cu ft/min); stress, cold, and current push it up. Track it dive after dive — a falling SAC rate is one of the clearest signs your diving is improving.