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SAC Rate Calculator
Surface Air Consumption — plan your gas requirements with confidence
🤿 SAC (Surface Air Consumption) Rate measures your breathing efficiency at the surface — essential for dive planning
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litres per minute (lpm)
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RMV Rate (at depth)
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Total Air Used
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Ambient Pressure (ATA)
📉 10 metres (33 ft)
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📉 15 metres (50 ft)
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📉 20 metres (66 ft)
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📉 30 metres (100 ft)
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| Depth (m) | Depth (ft) | Pressure (ATA) | Air Consumption (lpm) | Air Consumption (cfm) |
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⚠️ DIVE SAFETY DISCLAIMER
This calculator provides estimates for informational purposes only. UNDER NO CIRCUMSTANCES should this be used as the sole basis for dive planning. Always follow proper gas management protocols, maintain adequate reserves, and consult with a certified dive professional. Improper gas planning can result in serious injury or DEATH.
This calculator provides estimates for informational purposes only. UNDER NO CIRCUMSTANCES should this be used as the sole basis for dive planning. Always follow proper gas management protocols, maintain adequate reserves, and consult with a certified dive professional. Improper gas planning can result in serious injury or DEATH.
Calculate your Surface Air Consumption (SAC) rate — essential for dive planning
What is SAC Rate?
Surface Air Consumption (SAC) rate measures how much breathing gas you consume per minute at the surface. It's the fundamental metric for dive planning — once you know your SAC rate, you can calculate gas requirements for any depth and dive duration.
SAC Rate Formula
Metric: SAC (lpm) = ((Gas Used × Cylinder Size) ÷ ((Depth ÷ 10) + 1)) ÷ Time
Imperial: SAC (cfm) = ((Gas Used ÷ 14.7) × Cylinder Size) ÷ ((Depth ÷ 33) + 1) ÷ Time
How to Use This Calculator
- Time at depth: Duration of the dive segment you're analyzing (minutes)
- Average depth: Your average depth during that segment (metres or feet)
- Gas used: Pressure consumed — starting pressure minus ending pressure (bar or psi)
- Cylinder size: Water capacity in litres (metric) or tank rating in cubic feet (imperial)
Why Your SAC Rate Matters
- ✅ Gas Planning: Calculate how much gas you'll need for any planned dive
- ✅ Fitness Indicator: Track improvements in breathing efficiency over time
- ✅ Stress Detection: Higher SAC rates can indicate stress, cold, or current
- ✅ Equipment Optimization: Streamlining gear reduces drag and improves SAC
Factors Affecting SAC Rate
- Fitness Level: Fit divers typically have lower SAC rates (10-14 lpm)
- Stress & Anxiety: Nervous divers can breathe 2-3x more than relaxed divers
- Water Temperature: Cold water increases metabolic demand and SAC rate
- Current: Swimming against current significantly increases consumption
- Experience: New divers often have SAC rates of 18-25 lpm; experienced divers 10-15 lpm
- Body Size: Larger individuals typically have higher oxygen demands
Typical SAC Rate Ranges
- Excellent: 8-10 lpm (0.28-0.35 cfm) — Very efficient, relaxed diver
- Good: 10-14 lpm (0.35-0.5 cfm) — Typical experienced diver
- Average: 14-18 lpm (0.5-0.64 cfm) — Recreational diver with some experience
- High: 18-25 lpm (0.64-0.88 cfm) — New diver or working in current
- Very High: 25+ lpm (0.88+ cfm) — Stress, cold, or strong current
Gas Planning Rule of Thumb
For recreational diving, use the "Rule of Thirds": one-third for the dive, one-third for reserve, one-third for emergency. Always calculate based on your actual SAC rate, not averages.
Frequently Asked Questions
- What is a good SAC rate? — For experienced divers, 10-14 litres per minute is considered good. Beginners often start at 18-25 lpm.
- How do I lower my SAC rate? — Improve buoyancy control, streamline gear, stay warm, relax, and dive more frequently.
- What's the difference between SAC and RMV? — They're often used interchangeably, but RMV (Respiratory Minute Volume) technically refers to gas consumption at depth.
- How accurate is this calculator? — It uses standard formulas; accuracy depends on accurate input data.