Calculate your Surface Air Consumption for better dive planning.
Your Dive Metrics:
SAC Rate:—
RMV (Respiratory Minute Volume):—
Understanding SAC Rate and RMV
Surface Air Consumption (SAC) rate is a measure of how much gas a diver consumes at the surface, expressed in PSI per minute. Respiratory Minute Volume (RMV) is the volumetric equivalent, usually expressed in cubic feet per minute. Knowing these numbers is critical for gas management and dive planning.
The Calculation Logic
To find your SAC rate, we first determine your depth in Atmospheres Absolute (ATA):
ATA = (Depth / 33) + 1
Then, we calculate the gas consumption rate at depth and normalize it to the surface:
SAC Rate = (Gas Consumed / Time) / ATA
Realistic Example
If you dive to 66 feet (3 ATA) for 30 minutes and consume 1500 PSI using a standard AL80 tank (80 cu ft at 3000 PSI):
Consumption at Depth: 1500 / 30 = 50 PSI/min
SAC Rate: 50 / 3 = 16.67 PSI/min
RMV: (16.67 × 80) / 3000 = 0.44 CuFt/min
Why Your SAC Rate Matters
A lower SAC rate generally indicates better buoyancy control, more efficient movement, and a calmer breathing pattern. By tracking your SAC rate over multiple dives, you can accurately predict how long a tank will last at a specific depth, which is vital for planning deep or overhead environment dives.
function calculateSacRate() {
var depth = parseFloat(document.getElementById("diveDepth").value);
var gasUsed = parseFloat(document.getElementById("gasUsed").value);
var time = parseFloat(document.getElementById("diveTime").value);
var tankSize = parseFloat(document.getElementById("tankVolume").value);
var workingPressure = parseFloat(document.getElementById("workingPressure").value);
if (isNaN(depth) || isNaN(gasUsed) || isNaN(time) || isNaN(tankSize) || isNaN(workingPressure) || time <= 0 || workingPressure <= 0) {
alert("Please enter valid numbers in all fields.");
return;
}
// 1. Calculate ATA (Atmospheres Absolute)
var ata = (depth / 33) + 1;
// 2. Calculate SAC Rate (PSI/min)
// Formula: (Pressure Consumed / Time) / ATA
var sacRate = (gasUsed / time) / ata;
// 3. Calculate RMV (CuFt/min)
// Formula: (SAC Rate * Tank Volume) / Working Pressure
var rmv = (sacRate * tankSize) / workingPressure;
// Display Results
document.getElementById("sacResult").innerText = sacRate.toFixed(2) + " PSI/min";
document.getElementById("rmvResult").innerText = rmv.toFixed(2) + " CuFt/min";
// Provide simple analysis
var analysis = "";
if (rmv = 0.4 && rmv 0.6 && rmv <= 0.8) {
analysis = "Average air consumption. Focus on buoyancy and slow, deep breathing to improve.";
} else {
analysis = "High air consumption. This may be due to heavy workload, cold water, or stress.";
}
document.getElementById("analysisText").innerText = analysis;
document.getElementById("results-area").style.display = "block";
// Smooth scroll to results
document.getElementById("results-area").scrollIntoView({ behavior: 'smooth', block: 'nearest' });
}