SAC Rate Calculator
Compute your Surface Air Consumption (SAC) rate using average depth, starting and ending cylinder pressure, and total dive time. Assumes a cylinder size of your choice and ambient pressure from depth (P = 1 + D/10).
How to use the SAC rate calculator
Enter your average depth for the dive, your cylinder's start and end pressure, the dive time, and either pick a cylinder preset or enter a custom size in litres. Hit Compute.
The calculator first works out how much gas you used at depth (pressure drop × cylinder size, divided by dive time), then divides that by the ambient pressure at your average depth to normalize it to a surface rate — the SAC figure shown. Because it uses your average depth for the whole dive, it's most accurate for roughly square dive profiles; a dive with very uneven depth will skew the result.
FAQ
What is a good SAC rate?
Most recreational divers land somewhere around 15–20 L/min (0.5–0.7 cuft/min) at the surface once they're comfortable in the water; experienced technical divers with good buoyancy and trim are often lower. There's no single 'correct' number — it depends on your fitness, experience, exertion level, and even water temperature and stress on a given dive. The useful thing is tracking your own SAC rate over time and dives, not comparing it to someone else's.
What's the difference between SAC and RMV?
SAC (Surface Air Consumption) is usually expressed as pressure used per minute at the surface (e.g. bar/min or psi/min), while RMV (Respiratory Minute Volume) is expressed as a volume per minute (litres/min or cuft/min) independent of any particular cylinder size. This calculator reports the volumetric figure — multiply pressure-per-minute by your cylinder's liters-per-bar (or use this calculator directly) to convert between the two.
How do I calculate my SAC rate manually?
Work out the gas you used in the cylinder's own units (pressure drop × cylinder size), divide by dive time to get a consumption rate at depth, then divide that by the ambient pressure at your average depth (1 + depth/10 in metres) to normalize it back to what you'd use at the surface. That's exactly what this calculator automates from your entered depth, pressures, dive time, and cylinder size.