How Can I Decrease My SAC Rate?
A good SAC rate is part of being a great diver! There are many things you can do to improve your SAC rate. Many of these suggestions are topics on to themselves and we even have an entire course, much of which is devoted to helping you achieve a lower SAC rate. Below are the top 4 things you can do to decrease your SAC rate.
Master your Buoyancy
If you are struggling to stay down because you don’t have enough ballast or have too much ballast and are kicking just to stay off the bottom, then you are surely wasting energy and driving your SAC rate up. Doing a proper buoyancy check, learning where your dump valves are, and mastering buoyancy are the first steps toward a lower SAC rate.
Learn how to trim your body out properly.
If you are not trimmed out properly in the water, you’ll consume more energy throughout the dive. Notice in the illustration below how the diver to the left encounters more resistance as she tries to kick. This is because she isn’t trimmed out efficiently.
The frog kick and the modified frog kick require less energy than the flutter kick when you are diving. Because these kicks have a resting phase built-in you end up kicking less to cover the same distance underwater. Mastering the frog kick and the modified frog kick are one of the things you can do to help to lower your breathing rate.
Become More Comfortable Underwater
Your mental state plays a larger role in your breathing rate than most people realize. If you are not completely comfortable underwater it’s likely that your heightened state of anxiety will also raise your breathing rate. Being comfortable with all the basics of SCUBA diving including mask removal and replacement and buddy breathing, in case of emergency, are just the beginning. As you gain experience and become completely comfortable with being underwater your breathing rate will become lower.
How To Calculate SAC Rate (Formula)
You might be wondering, how are the numbers given by the calculators computed? Below is the explanation so you can understand the math and how the SAC rate works.
Imperial System SAC Rate Calculation
Computing your SAC rate is fairly straight forward. Remember to follow the guidelines in this article best practices for calculating your SAC / RMV. You can calculate your SAC rate in 3 easy steps. To do so, you’ll need the following:
- Average depth during the test
- Starting and ending PSI during the test
- The amount of time you conducted your SAC rate test for
Let’s assume the following variables for our example:
- Depth = 55 Feet (Saltwater)
- Starting PSI = 2700, Ending PSI = 1800
- Time of Test = 15 minutes
Step 1: Figure out your depth in atmospheres absolute. In this example we assume a dive in saltwater, so we use 33 feet as an atmosphere. If you are diving in freshwater, you’d use 34 feet to calculate an atmosphere. To figure out your depth in atmospheres absolute (ATA) divide your depth by 33 and add 1 to it. So, if for example, you dived to 55 feet, you’ll divide 55 by 33 and add 1. So (55/33) + 1 = 2.68. 2.68 = Your depth in atmospheres absolute (ATA)
Step 2: Figure out how much gas you used in PSI. Assuming you started your test with 2700 PSI and you ended up with 1800 PSI, it means you consumed 900 PSI during your test. 2700 PSI-1800 PSI= 900 PSI.
Step 3: Divide the total PSI used by your ATA and then by the total number of minutes you did the test for. So (900/2.68 = 335.82) and (335.82/15 = 22.38). This gives you your SAC rate. So your SAC rate for this example is 22.38 PSI per minute.
The Formula for calculating your SAC rate is.
((Starting PSI – Ending PSI) / Depth in ATA) / Duration of test) = SAC Rate
*Remember that your SAC rate is dependent on the cylinder you used. Your SAC rate will be different if you use a different cylinder.
Metric System SAC Rate Calculation
Computing your SAC rate is fairly straight forward in the metric system. Remember to follow the guidelines in this article best practices for calculating your SAC / RMV. You can calculate your SAC rate in 3 easy steps. To do so, you’ll need the following:
- Average depth during the test
- Starting and ending BAR during the test
- The amount of time you conducted your SAC rate test for
Let’s assume the following variables for our example:
- Depth = 17 Meters (Saltwater)
- Starting pressure in BAR = 190, Ending pressure in BAR = 120
- Time of Test = 15 minutes
Step 1: Figure out your depth in atmospheres absolute. To figure out your depth in atmospheres absolute (ATA) divide your depth by 17 Meters By 10 and add 1 to it. So, if for example, you dived to 17 meters, you’ll divide 17 by 10 and add 1. So (17/10) + 1 = 2.7. 2.7 = Your depth in atmospheres absolute (ATA)
Step 2: Figure out how much gas you used in PSI. Assuming you started your test with 190 BAR and you ended up with 120 BAR, it means you consumed 70 BAR during your test. 190 BAR -120 BAR = 70 BAR.
Step 3: Divide the total pressure in BAR you used by your ATA and then by the total number of minutes you did the test for. So (70/2.7 = 25.92) and (25.92/15 = 1.72). This gives you your SAC rate. So, your SAC rate for this example is 1.72 BAR per minute.
The Formula for calculating your SAC rate is.
((Starting BAR – Ending BAR) / Depth in ATA) / Duration of test) = SAC Rate
*Remember that your SAC rate is dependent on the cylinder you used. Your SAC rate will be different if you use a different cylinder.
Do you know your SAC Rate? How do you plan to calculate and use this number? Let us know in the comments below.