SAC / RMV Calculator for Scuba Diving

How to Use This SAC / RMV Calculator

This calculator uses data from a real dive you have already done to estimate your personal gas consumption at the surface.

To get the most accurate result, use your dive computer’s average depth, not maximum depth.

You will need:

  • Your average depth for the dive
  • Your bottom time in minutes
  • Your starting tank pressure
  • Your ending tank pressure
  • Your cylinder’s internal volume (e.g. 12 L steel, or AL80 ≈ 11.1 L)

Steps:

  1. Enter your average depth and select metres or feet
  2. Enter your bottom time in minutes
  3. Enter your start and end pressure (bar or psi)
  4. Enter your cylinder size (internal volume)
  5. Click Calculate

The calculator will show:

  • Your SAC (Surface Air Consumption) in bar/min and psi/min
  • Your RMV (Respiratory Minute Volume) in litres/min and cubic feet/min

Tip: For planning purposes, calculate this from several relaxed dives and use the highest or average value. Always plan conservatively for cold water, current, stress, or task loading.

This tool is for educational planning only and does not replace dive training, dive tables, or a dive computer.

Enter the details from a real dive log to calculate your personal air consumption.

SAC / RMV Calculator for Scuba Diving

Calculate your SAC (Surface Air Consumption) and RMV (Respiratory Minute Volume) from a single dive log. Works for bar/psi and metric/imperial.

Safety note: This calculator is for educational planning only. Do not use as a substitute for dive tables, a dive computer, or professional training.

1) Dive Log Inputs

Use your dive computer’s average depth if available.
minutes
Time between starting descent and beginning final ascent.
bar
Pressure when you ended the working portion of the dive.

2) Cylinder Inputs

Example: AL80 is ~11.1 L internal volume (approx).
bar
Optional. If you enter working pressure, we’ll estimate gas volume for cu ft users more accurately. If blank, we use standard conversions.

Quick FAQ

What’s the difference between SAC and RMV?

SAC is pressure drop at the surface (bar/min or psi/min). RMV is the actual gas volume you breathe at the surface (L/min or cu ft/min). RMV is usually best for planning because it stays comparable across cylinder sizes.

Should I use average depth or max depth?

Use average depth from your dive computer if you have it. If not, estimate your average depth from your dive profile (not max depth).

What’s a “good” RMV?

It varies widely. Many relaxed divers might be around 12–20 L/min at the surface, while stressed or high-workload diving can be much higher. Use your own measured RMV and plan conservatively.

Does this replace my dive computer or gas planning training?

No. This is for educational planning only. Always dive within your training, use a dive computer/tables, and follow your instructor/agency standards.

How to Improve Your SAC / RMV

Your SAC and RMV are not fixed numbers — they change with technique, conditions, equipment, and stress level. If you want to reduce your gas consumption and extend your dive time, focus on these fundamentals:

1) Improve buoyancy and trim

Poor buoyancy and bad body position create constant drag and unnecessary finning. Good horizontal trim and relaxed buoyancy control reduce effort and air usage dramatically.

2) Slow down your finning and movements

Fast finning, sculling with the hands, and unnecessary movement all increase workload. Move slowly and deliberately and let momentum work for you.

3) Relax and control your breathing

Stress and task loading increase breathing rate immediately. Focus on slow, deep, relaxed breathing and avoid breath-holding or rapid shallow breathing.

4) Streamline your equipment

Dangling hoses, accessories, and bulky setups increase drag. A clean, streamlined kit reduces effort and air consumption, especially in current.

5) Dive within your comfort zone

Cold water, current, poor visibility, and task-heavy dives all increase gas usage. Plan conservatively and expect a higher RMV in demanding conditions.

Tip: Track your RMV over several relaxed dives and use the highest realistic value for planning future dives.

⚠️ Important Safety Note

Lower gas consumption is not a goal by itself. Safe, controlled diving with good buoyancy, awareness, and reserve gas is always more important than chasing a lower number.

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