Buoyancy & Weighting:
How to Calculate Proper Weighting for Scuba Diving

What Is Buoyancy and Why Does It Matter?

Buoyancy is the force that determines whether you float, sink, or stay neutral in the water. For scuba divers, proper weighting is critical for maintaining control, conserving air, and executing safe ascents and descents.

Many divers struggle with buoyancy because their weighting is incorrect. If you are too light, you can’t stay down. If you are too heavy, you waste energy and air compensating with your BCD. Getting your weighting right is the foundation of good buoyancy control.

The Danger of Too Much or Too Little Weight

Incorrect weighting can lead to serious problems underwater:

Too Little Weight

• Difficulty descending at the start of a dive.
• Inability to hold a safety stop at 15 feet.
• Increased risk of uncontrolled ascent, leading to decompression issues.

Too Much Weight

• Rapid descents, increasing the risk of barotrauma.
• Over-reliance on the BCD, leading to buoyancy instability.
• More effort needed to control position, increasing air consumption.

How to Perform a Pre-Dive Weight Check

The pre-dive weight check is a quick way to get an initial estimate of your weighting:

1. Put on all your dive gear and enter the water.
2. Release all air from your BCD.
3. Take a normal breath and float at eye level.
4. Exhale fully—you should start to sink slowly.

Note: This check does not account for the weight of the gas you will consume during the dive. If you rely on this method, you may be underweighted at the end of the dive.

The Post-Dive Weight Check: The Most Accurate Method

To determine your true weighting, perform this test at the end of a dive:

1. At the end of a dive, ascend to 15 feet with 500 PSI (or your usual reserve pressure).
2. Empty all air from your BCD and drysuit if you are wearing one.
3. Take a normal breath—you should float slightly up.
4. Exhale—you should sink slightly down.

If you are too heavy, remove some weight before your next dive. If you are too light, add weight.

Using Math to Calculate Your Weighting (For Precision)

If you want to determine your weighting scientifically, follow these steps:

1. Find your personal buoyancy by floating in a pool wearing only a swimsuit. Add weight until you sink.
2. Test your exposure suit by wearing it without gear and adding weight until you sink.
3. Measure the buoyancy of each piece of your equipment (BCD, tank, regulators) using a fish scale.
4. Add up all values to calculate how much weight you need to offset positive buoyancy.

This method allows for precise weighting adjustments and helps avoid unnecessary trial and error.

Adjusting for Saltwater vs. Freshwater

Saltwater is denser than freshwater, meaning you need more weight to descend. A general rule:

• Add 5-6 lbs when switching from freshwater to saltwater.
• Adjust as needed based on actual buoyancy tests.

Final Thoughts: Mastering Your Buoyancy

Getting your weighting right is essential for better buoyancy control, lower air consumption, and safer dives. Now that you know how to determine your weighting, the next step is learning how to distribute that weight properly.

Read more about setting up a Balanced Rig to optimize weight placement.