SAC / RMV Calculator

SAC / RMV — Key Features

• Calculate SAC rate from tank specs, depth, time, and pressure used
• Results in liters/min (metric) or cubic feet/min (imperial)
• Interpretation guide — from excellent to needs improvement
• Essential for accurate dive gas planning
• Works with any tank size and gas mix
• Support for both metric and imperial units

SAC / RMV — How It Works

Enter your tank volume, start and end pressure, average depth, and dive time. The calculator normalizes your gas consumption to surface pressure, giving you your SAC rate. Track your SAC over multiple dives to get an accurate personal baseline for gas planning.

Why Know Your SAC Rate?

• Accurately predict gas consumption for future dives
• Plan appropriate tank sizes for different dive profiles
• Track improvement in your air consumption over time
• Essential input for rock bottom and emergency gas calculations

SAC / RMV — Frequently Asked Questions

What is SAC rate?

SAC (Surface Air Consumption) or RMV (Respiratory Minute Volume) is your gas consumption rate normalized to surface pressure. It represents how much gas you would breathe per minute at the surface and is used to predict consumption at any depth.

What is a good SAC rate?

For recreational divers, a typical SAC rate is 15-20 L/min. Below 15 L/min is considered excellent, while above 20 L/min suggests room for improvement through relaxation techniques and better trim.

Why does SAC matter for dive planning?

Knowing your SAC rate lets you calculate exactly how much gas you'll need for a given dive profile. It's essential for planning decompression dives, calculating rock bottom reserves, and choosing the right tank size.

How do I measure my SAC rate underwater?

Note your starting pressure, depth, and time at the beginning of a segment at constant depth. After several minutes, record your ending pressure. Enter these values along with your tank size into the calculator to get your normalized surface consumption rate.

What is the difference between SAC and RMV?

SAC (Surface Air Consumption) is typically expressed in bar per minute at the surface, while RMV (Respiratory Minute Volume) is expressed in liters per minute. They represent the same concept — your gas consumption normalized to surface pressure — just in different units.

Does my SAC rate change over time?

Yes. New divers typically have SAC rates of 20-25 L/min, which improve with experience as buoyancy, trim, and relaxation get better. Experienced divers often achieve 10-15 L/min. Tracking your SAC rate over time helps monitor your progress as a diver.