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Calcimator

Scuba Air Consumption Calculator

Calculate your surface air consumption (SAC) rate and estimate remaining bottom time at depth based on tank size and pressure readings.

Inputs

gal
bar
bar
min
ft

Results

SAC Rate

10.71 L/min

Consumption at Depth30 L/min
Bottom Time Remaining20 min
Rate Rating1
How to Use This Calculator
  1. Enter your tank volume in liters (e.g., 12 L for a standard single cylinder).
  2. Input the starting pressure in bar and ending pressure in bar from your dive computer or SPG.
  3. Enter the total dive duration in minutes.
  4. Set the average dive depth in meters for the Boyle's Law depth correction.
  5. Read your SAC Rate (Surface Air Consumption) in L/min — below 12 is excellent; 15–20 is typical for recreational divers.
  6. Use Remaining Bottom Time to plan your gas reserve when diving the same profile again.

How the result changes with Start Pressure

Start PressureSAC Rate
75-2.68 L/min
1384.07 L/min
21312.11 L/min
27518.75 L/min

What each input means

Tank Volume
Internal water volume of your scuba tank. Standard aluminum 80 = 11.1L, steel HP100 = 12.9L.
Start Pressure
Tank pressure at the beginning of your dive. A full aluminum 80 is ~207 bar, steel HP100 is ~230 bar.
End Pressure
Tank pressure at the end of your dive or measurement period.
Dive Duration
Total time underwater in minutes, from descent to the reading point.
Average Depth
Average depth of the dive in meters. Use your dive computer's average depth reading for best accuracy.

What each result means

SAC Rate
Surface Air Consumption rate — your air use normalized to surface pressure. Lower is better; 12-15 L/min is average.
Consumption at Depth
Actual air consumption rate at the specified depth, accounting for increased ambient pressure.
Bottom Time Remaining
Estimated minutes remaining at this depth with current air, keeping a 50-bar safety reserve.
Rate Rating
1 = Excellent (<12), 2 = Average (12-17), 3 = High (17-22), 4 = Very High (>22 L/min).

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Tank Volume = 12, Start Pressure = 200, End Pressure = 100, Dive Duration = 40 = 5 input(s) provided
  2. Calculate SAC Rate
    SAC Rate
    10.71 = 10.71
  3. Calculate Consumption at Depth
    Consumption at Depth
    30 = 30
  4. Calculate Bottom Time Remaining
    Bottom Time Remaining
    20 = 20

Engine last updated . Checked against 2 independently-derived tests — how we verify calculators.

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