An important part of preparing for each dive is calculating the amount of weight you’ll need to ascend and descend safely and effectively. By gearing up in the correct amount of weight, you can successfully maintain neutral buoyancy throughout the dive.
There are many factors that can affect your buoyancy—your body composition, the equipment and clothing worn, the amount of air you’re breathing, and the water you’ll be swimming in (freshwater versus saltwater), etc. Being able to add weights to your scuba weight belt or in the pockets of your BCD can not only make dives safer but will also minimize drag and promote more efficient finning. Without them, you would be bobbing like a cork or dropping like a stone when you get into the water.
Needless to say, proper weighting and buoyancy control is crucial if you want to have an enjoyable dive. Unfortunately, there’s no plug and chug math formula you can use to calculate exactly how much weight you’ll need, so getting it just right requires knowledge and practice. To help make it easier, below are a few easy steps you can take, preferably with the assistance of a dive weight calculator.
Steps to Calculating Your Dive Weight
A rough approximation of the weight you’ll need can be figured out quickly by weighing yourself and then using those numbers to figure out the amount of weight you’ll need on you.
In freshwater, most divers need 6 to 8 percent of their body weight in added weight, whereas in saltwater (which is denser and will add buoyancy), this figure is closer to 8 to 10 percent. This number is a good starting point to further calculate your weight amount.
Weigh Your BCD
Part of determining your body weight is weighing your buoyancy compensator (BCD) or dive jacket. It is a major source of buoyancy as most of them, especially older models, have a lot of padding that will make you float.
To determine the buoyancy of your BC, immerse it in water and release any air that might be trapped inside. Make sure you open all the exhaust valves, press all the padded areas, and gently rotate the jacket to allow all air to escape.
When there are no longer any bubbles rising to the surface, let go of the BC. If it comes to the surface, add weight until it is able to hang in the water. Note how much weight was required to make it neutrally buoyant in the water.
Consider Your Equipment
Some beginners think that wearing more clothes, in addition to their gear, will make them heavier in the water. As it turns out, protective clothing (like wetsuits) can actually make you float.
If you’re wearing a full wetsuit, or one thicker than 3-4 mm, you’ll need to compensate by adding more dive weights, as both of these will make you more buoyant. Conversely, if you’re diving in just a bathing suit or shorts, you’ll need less weight.
Also, consider the weight of your other equipment—everything from your tank and fins to your dive knife and scuba computer. You’ll be surprised how small items can contribute to your overall buoyancy.
Test Your Weight
Finally, it’s time for you to get into the water. Go through a trial run in a swimming pool and wear all of your dive gear.
If you can’t wear your full equipment, make sure to put on the closest approximation to what you’ll be wearing for the specific dive. Next, try on several different amounts of dive weights; you’ll be able to get a better feel for the amount and number of dive weights you’ll need this way.
Remember that if your dive is going to be in saltwater, you’ll need a bit more weight compared to a freshwater swimming pool.
Adjust As Needed
Should you run into any buoyancy problems mid-dive, always make a note in your dive log or even your underwater writing device. If you realize you were sinking, write down the amount of weight and take less next time. If you couldn’t descend, write down the amount of weight and experiment with more to find an amount that affords you control over your depth.
Use a Scuba Weight Calculator
While manually figuring out the right amount of dive weights to gear up in works for many divers, others find it easier to use an actual calculator. Try using a scuba diving weight calculator in kg (or in imperial units), if you’re used to measuring in kilograms. You’ll be able to find tons of calculator websites online. Simply enter the figures for the required fields and check if the suggested amount of weight works for you. Find a calculator that works for you and stick to that, but make sure you test yourself before each dive!