When you’re preparing for your next scuba diving adventure, one of the key things you’ll have to consider is how much weight you need to carry. Having the right amount of weight is crucial for a safe and enjoyable dive. Too little weight, and you’ll struggle to descend or worse you may not be able to hold your safety stop in the end of the dive because you are too buoyant. Too much weight, and you’ll find it hard to control your buoyancy or may not even be able to hold yourself comfortable on the surface. So, how do you figure out just the right amount?
The amount of weight you need depends on a variety of factors, including your tank material, salt or fresh water, your dive suit, and your overall buoyancy characteristics. Let’s dive deeper into each of these elements to help you determine how much weight is right for you!
Tank Material: Aluminium vs. Steel
The material of your tank plays a significant role in determining how much weight you need. Tanks most commonly come in two materials: aluminium or steel. Both of these materials have different buoyancy characteristics, which influence how much weight you’ll need to balance your buoyancy.
- Aluminium Tanks: These are less dense than steel tanks and typically lighter underwater. As a result, they tend to be slightly positively buoyant, which means they want to float. For most divers, this means adding more weight to counteract the buoyancy and help you sink to your desired depth. Compared to a similiarly sized steel tank you want to add 2-3kg.
- Steel Tanks: On the other hand, steel tanks are denser and tend to be negatively buoyant. This means they are naturally inclined to sink, so you may need less weight to balance out your buoyancy.
Steel tanks also maintain their buoyancy characteristics better throughout the dive (always negative), while aluminium tanks can become more buoyant as they empty. They start negative and become buoyant when going from 200 to 50 bar.
In practice, the type of tank you use will have an impact on the weight you need. If you’re using an aluminium tank, you’ll likely need more weight to compensate for its positive buoyancy. If you’re using a steel tank, you may be able to reduce your weight, as the tank itself will naturally help you descend.
Generally, steel tanks are used in colder climate where we need more weight anyway and aluminium tanks in warmer regions (asia, south america, …) where we need less weight.
Tank Size Doesn’t Typically Influence Weight Requirements
It’s common to think that a larger tank would require more weight. In most cases, the size of the tank doesn’t significantly impact how much weight you need. While a larger tank like a 15L weighs more than a 12L tank, it is also bigger, so it displaces more water. There is always differences between different tank manufacturers but generally speaking a 12L and a 15L have more or less the same buoyancy, so when switching tanksizes for different dives you do NOT need to switch your weight.
What is true for bigger tanks or even configuration with two tanks (sidemount or twinsets) is that when using bigger or more tanks your change in buoancy will be bigger, because you use more gas. To give an example, when we dive a 12L tank from 200 to 50 bars we use up 1800L of air which weighs around 2.15kg, so you will be 2.15kg lighter in the end of the dive.
When doing the same to a 15L tank the change will be 2250L or 2.7kg. For a twinset of 2x12L the change will be exactly double 4,3kg, because you basically empty two tanks at the same time.
This is something to keep in mind when diving these tank-configurations and calculating your minimum and maximum weight!
The Impact of Dive Suit Thickness on Weight Requirements
The thickness of your dive suit is one of the most important factors in determining how much weight you need. A thicker suit provides more insulation but also traps more air, which makes you more buoyant.
- Wetsuits: If you’re diving in warm water with a thinner wetsuit (e.g., 3mm), you won’t need as much weight because the suit isn’t providing a lot of buoyancy. However, if you’re diving in colder water with a thicker wetsuit (e.g., 7mm), you’ll need to add much more weight to offset the buoyancy created by the suit. You will also notice that the buoyancy of your suit decreases over time, as it wears out. I once bought the exact same model of a 7/8mm suit again and had to add 2kg to my weight because of the difference between old and new!
- Drysuits: If you’re using a drysuit, which is more buoyant than a wetsuit, you’ll definitely need more weight. Drysuits trap air to keep you warm, which significantly increases your buoyancy, especially as you descend. Divers who use drysuits often need several extra kilograms of weight to compensate for this compared to a wet suit. The amount of weight you need depends highly on the undergarment you wear under your drysuit. Generally speaking: colder water → thicker undergarment → more weight needed.
Personal Buoyancy and Body Composition
Every diver has a different body composition, and this can influence how much weight is required. For instance, a diver with a higher body fat percentage may have more natural buoyancy, meaning they’ll need more weight to counterbalance that. Conversely, a more muscular diver, who is denser, may need less weight.
In general and from our day-to-day experience (there are always exceptions!) this means that women tend to need a bit more weight than men, assuming the same weight and size.
Here on Tenerife we roughly count 1kg of weight per 10kg of bodyweight, so for a person of 80kg a weight belt of 8kg would be appropriate. But this is just a very rough estimate, I have had super muscular clients with 80kg+ who did not need any weight at all!
But in the end the only way to really know how much weight you need is to test it in the water.
Other Factors to Consider
There are a few other factors to keep in mind when calculating the right weight for your dive:
- Saltwater vs. Freshwater: Saltwater is denser than freshwater, which means you’ll be more buoyant in saltwater. If you’re diving in the ocean, you will need slightly more weight compared to diving in freshwater lakes or quarries. The higher the salinity, the denser the water—so in places like the Red Sea, you may need even more weight than in other saltwater locations.
- Weight Belt vs. Integrated Weight: Some dive equipments, like buoyancy control devices (BCDs), come with integrated weight systems that distribute the weight more evenly across your body, improving your trim. This can be more comfortable than a traditional weight belt. It’s important to check your equipment to ensure it’s set up for optimal comfort and safety.
How to Find Your Ideal Weight
The best way to figure out how much weight you need is to perform a weight check before your dive in a new environment or when you have new gear. Here’s a simple method we teach in the PADI OWD course to do so, it is best to do this check in the end of the dive with an empty tank (50 bars):
1. Make sure you have your scuba mask on your face & your regulator in your mouth
2. At the surface deflate your BCD fully while holding your breath
3. While holding a full breath with a deflated BCD, you should float at eye level
(if you sink you carry too much weight)
4. When you breath out you should go down slowly
(if you don’t descent, you need more weight)
This is a basic check to see if you carry the correct weight. In the end it is important to make sure you have enough weight, but not too much.
The minimum amount of weight you need is in the end of the dive (with empty tank = 50 bars) to be able to hold your stop at 3-5m comfortably with a nearly empty BCD without going up.
Too much weight is when you are not able to hold yourself comfortably on the surface (in the beginning of the dive when you are the heaviest), even with an inflated BCD. But you really should never take much more weight with you than you really need. Why?
Because you could also have a BCD failure and then you need to fin with your own legs against the negative buoyancy to the surface, so less negative buoyancy is much better for your safety!
If you’re unsure about the right amount of weight for your dive or need more detailed guidance on buoyancy control, our dive instructors are always happy to assist. We’re here to help ensure that you dive safely and comfortably.
Conclusion
The amount of weight you need for scuba diving is influenced by various factors, such as your tank material, the thickness of your dive suit, and your body composition. It’s important to consider these elements and perform a proper weight check before heading out on a dive to ensure you have the right amount of weight to stay safe and enjoy your underwater experience. Always remember that having the right buoyancy control will make your dive more enjoyable and efficient, helping you focus on the beauty of the underwater world.
Happy diving!
