RMV Calculator – Respiratory Minute Volume & SAC Rate
Calculate your Respiratory Minute Volume (RMV) and Surface Air Consumption (SAC) rate for scuba dive planning. Enter your dive data and tank info for an instant result.
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What is RMV (Respiratory Minute Volume)?
Respiratory Minute Volume (RMV) – also known as Surface Air Consumption (SAC) rate – is the amount of gas a diver breathes per minute at the surface. It is a key metric for scuba dive planning because it lets you estimate how long your gas supply will last at any given depth.
How to calculate RMV
RMV is calculated by dividing the total gas consumed (in litres or cubic feet) by the dive time and the ambient pressure at average depth. The formula is: RMV = Gas consumed ÷ (Time × Ambient pressure). Ambient pressure equals depth ÷ 10 + 1 (metric) or depth ÷ 33 + 1 (imperial).
What is a good RMV / SAC rate?
A typical RMV for recreational divers ranges from 15 to 20 litres per minute (0.5–0.7 cuft/min). Experienced divers often achieve 12–15 L/min. Higher values may indicate stress, heavy exertion, or inefficient breathing technique. Tracking your RMV over multiple dives helps you plan gas more accurately and improve your air consumption.
RMV vs. SAC rate – what is the difference?
RMV and SAC rate describe the same concept – your breathing rate normalised to surface pressure. "RMV" (Respiratory Minute Volume) is the term commonly used in Europe and metric-based training agencies, while "SAC rate" (Surface Air Consumption) is more common in North America and imperial-unit contexts. This calculator supports both metric (bar/litres) and imperial (psi/cuft) units.
Frequently asked questions
▶ Why should I know my RMV?
Knowing your RMV lets you calculate how much gas you will need for a given dive profile. This is especially important for deeper dives, technical diving, and dive planning with multiple tanks. It helps you choose the right tank size and plan safe turn pressures.
▶ How can I improve my air consumption?
Slow, deep breathing, good buoyancy control, streamlined positioning, and regular diving practice all help reduce your RMV. Avoid unnecessary movement, stay relaxed, and breathe from your diaphragm rather than your chest.
▶ Can I use this calculator with multiple tanks?
Yes! Registered users can add up to 4 tanks (e.g. for twinsets, sidemount, or stage bottles). The calculator sums the gas consumed across all tanks. Guest users can calculate with one tank – register for free to unlock multiple tanks.
▶ What units does the calculator support?
The calculator supports both metric (depth in metres, pressure in bar, volume in litres) and imperial (depth in feet, pressure in psi, volume in cubic feet) units. Toggle between them using the Metric/Imperial switch at the top.