Respiratory Minute Volume (RMV) Calculator
Respiratory Minute Volume (RMV) tells you how much gas you breathe per minute at the surface, measured in cubic feet per minute (cuft/min). It’s one of the most useful numbers in scuba diving because it lets you estimate how much gas you’ll need for future dives at different depths. Unlike your SAC rate (which is PSI-based and tank-specific), RMV is tank-independent and lets you compare breathing rates across dives, divers, or conditions.
To calculate your RMV, you'll need:
Results
Common Scuba Tank Sizes
| Tank Name | Capacity (cuft) | Rated Pressure (PSI) |
|---|---|---|
| AL19 | 19.0 | 3000 |
| S40 | 40.0 | 3000 |
| AL80 (default) | 77.4 | 3000 |
| Double AL80 | 154.8 | 3000 |
| HP80 | 81.7 | 3442 |
| Double HP80 | 163.4 | 3442 |
| HP100 | 100.0 | 3442 |
| Double HP100 | 200.0 | 3442 |
| HP117 | 117.8 | 3442 |
| HP120 | 120.1 | 3442 |
Surface Air Consumption (SAC) and Respiratory Minute Volume (RMV)
- SAC rate describes gas consumption at the surface in pounds per square inch per minute (PSI/min) and is specific to that size cylinder. It is easy to calculate but cumbersome to use in future planning.
\[ SAC = \frac{(\frac{\text{Starting PSI} - \text{Ending PSI}}{\text{Dive Time in Minutes}})}{\text{Average Depth in ATA}} \]
- RMV rate describes gas consumption at the surface in cubic feet per minute (cuft/min) and adjusts for tank size, allowing consistent gas calculations across different cylinders.
\[ RMV = \text{SAC} \times (\frac{\text{Tank Size in cuft}}{\text{Tank Size in PSI}}) \]