How to Calculate Your Weight Belt Weight When Spearfishing

Spearfishing Weight Belt Calculator

If you are new to spearfishing a weight belt might be a new concept to you. If you’ve been spearfishing before, you are likely very aware of what it is.

Why Do You Need a Weight Belt When Spearfishing

Since most of the time when you go spearfishing you are going to be wearing a wetsuit, you are going to need a weight belt. This is because wetsuits are quite buoyant, and will prevent you from easily being able to dive to the bottom, this is where weight belts come in.

The most important thing about using a weight belt is knowing how much weight to use. Adding too little weight and you will have a hard time swimming to the bottom, adding too much and you can have much bigger problems. Before I dive deeper into this article, you need to instill in your head, it’s always better to have less weight than more weight when you’re testing weights. Having too much weight, even once, could be fatal. Always dive with a buddy, especially when testing new weights.

Factors that Affect How Much Weight To Put On Your Weight Belt

It’s important to note, the amount of weight you need on your dive belt with differ for countless reasons, the most common being:

  • The thickness of your wetsuit

  • What type of wetsuit do you wear while spearfishing

    • Does your wetsuit have a hood

    • Do you wear thick booties

  • How deep you are going to be diving

  • Where the fish in the water column are

  • The shape and composition of your body

  • Your spearfishing and diving experience

The general goal of adding a weight belt is to get you back to the neutral buoyancy you have when you are only wearing a bathing suit, and no wetsuit. What I mean by this, is with a bathing suit on and air in your lungs, you are going to float in the water. 

A Weight Belt Should Make You Comfortable

Picture being in a pool, if you are casually swimming around, you are able to float in the water, but you can also easily dive down. You won’t be fighting to get down as if you were wearing a wetsuit, or a life jacket. The small amount of buoyancy your lungs give you won’t be too much to keep you from going down. This is what you want.

However you want to make sure you are not wearing too much weight when you’re diving. Too much weight will of course make it very easy to get to the bottom, but it will make swimming back up much harder, and remember you will be swimming back up to the surface to catch your breath. You don’t want to have to be working hard to catch your breath.

Okay, now that you understand you will need different amounts of weights based upon a bunch of factors, let's get to calculating.

Calculating Dive Weights for Spearfishing

As I mentioned the goal of weight belts is to get you back to the buoyancy of wearing no floatation helper. 

Your wetsuit has a bunch of tiny bubbles of gas inside it which help you float. However, when you get about 26’ deep (8 meters), those gas bubbles are going to compress, and become much less buoyant. 

This means that after 26’ deep you are going to become less buoyant overall, and start falling towards the bottom. This is really nice, because it makes getting down to the bottom quite easy. The 26’ mark is the perfect mark because it will still keep you buoyant enough to make swimming back to the surface easy. As you head to the surface the bubbles will decompress, and you will become more buoyant making it easier to swim to the surface. 

It's also important to mention that if you are going to be diving only 10-20ft deep you may want more weight, this is because you you will want to reach the neutral mark earlier so you aren't being pushed up to the surface.

I tend to wear more weight when I'm spearfishing for striper bass from shore. As opposed to when I was spearfishing in the Florida Keys I used a higher ratio of weights to wetsuit because I was diving more than 26' deep. That's why It's imortant to think of every factor that you can when you go to set yourself up. The first dive of the season you may want to wear less weights while you are getting back into it.

Be careful, when you are testing weights out, and always have a dive buddy with you.

Getting the Right Amount of Weight for Your Weight Belt

Each person is going to be different based on a bunch of factors, but when you are doing your first calculation for weight, you can do the 2 kg measurement. To calculate this, take the thickness of your wetsuit and add 2 to it, to get your starting weight. For Example


  • 1mm Wetsuit = 1 + 2 = 3 kg / 6.6 lbs of weight on a weight belt
  • 1.5mm Wetsuit = 1.5 + 2 = 3.5kg / 7.7 lbs  of weight on a weight belt
  • 2mm Wetsuit = 2 + 2 = 4 kg / 8.8 lbs of weight on a weight belt
  • 3mm Wetsuit = 3 + 2 = 5 kg / 11 lbs of weight on a weight belt
  • 4mm Wetsuit = 4 + 2 = 6 kg / 12.2 lbs of weight on a weight belt
  • 5mm Wetsuit = 5 + 2 = 7 kg / 15.4 lbs of weight on a weight belt
  • 6mm Wetsuit = 6 + 2 = 8 kg / 17.6 lbs of weight on a weight belt
  • 7mm Wetsuit = 7 + 2 = 9 kg / 19.8lbs of weight on a weight belt

Adjusting Your Weight Belt Weight Based on Your Body

Please note, these estimates are based on a 175 lbs / 80 kgs man. If you weigh less, you are going to want to add 1.5 kgs to your wetsuit thickness instead of 2 kgs. Same thing goes if you’re much heavier, you will want to add 2.5 kgs to your wetsuit thickness, instead of only 2 kgs.

If you’re new to the sport, always use less weight first. It’s a lot easier to go diving and realize you need more weight, than to go diving and find yourself sinking in the water. Proceed with caution and always dive with a buddy.

Okay so now you’ve roughly calculated the weight you need to comfortably freedive and spearfish. Now it’s time to make sure you are using a good weight belt. 

How To Choose a Spearfishing Weight Belt

As you've been reading, getting the weight right on your weight belt is critical, but so is your weight belt itself. 

The number 1 thing to make sure your weight belt has, is a quick release. Having a quick release on your eight belt is important because it gives you the option to drop your weights instantly and gain buoyancy which will help you float to the surface and avoid danger. 

The good news is many brands make excellent weight belts with quick releases.

The other aspect of a weight belt is the material.

What Weight Belt Material is Best for Spearfishing

My father’s old weight belts were all nylon. This is what I started out using also, but we both came to learn of a far superior material for weight belts, rubber.

A rubber weight belt has a nice stretchiness that lets you tighten it more, and it grabs onto your body nicely. A nylon belt may be fine for scuba diving, but when you’re spearfishing a nylon belt is going to move all around you. When you go for your duck dive it will likely be moving all around your waist and stomach, you want to avoid this. 

While it can be okay for scuba divers, since they are not moving as much or as fast. Spearfishers need a rubber belt that will stay in place throughout their entire dive. 

Spearfishing Weight Belt Tips

The best tip I can give you for a weight belt is to keep the belt longer than it needs to be. What I mean is when you have the weight belt on, you want to have some extra belt material coming through the buckle. This long piece of belt gives you something to grab and pull forward which will open your quick release. The last thing you want underwater is to go to take your weight belt off, and not be able to get it off.

With saying this, make sure you don’t tuck the long end into your belt. I have seen too many spearfishers tuck in the end of their belt, this then makes it harder to grab the end and initiate the quick release, it also might prevent the quick release from working if the end is tightly tucked into your belt.

The image below isn't the best quality, but I circled the extra length you should leave on your weight belt to make it easy to pull the quick release.

Spearfishing Weight Belt Set up, Tips and Tricks

Attaching a Dive Knife to a Weight Belt

Once you have purchased a rubber weight belt, and calculated your correct weight. It’s time to add a dive knife to your belt. 

While some people prefer a knife holster and strap on their leg or arm, I prefer to have my knife on my weight belt. I find having a knife on my belt makes it easy to grab my knife and I don’t have to move at all. I tend to use my knife often when I am in rocks shooting fish. This is most prominent when I am spearfishing for Tautog. I like to brain the fish right after shooting them, many times while I am still underwater. This helps me secure the catch and not worry about them swimming into a hole in the rocks.

It’s important your dive knife has a good holster that is firmly attached to your weight belt, you do not want to lose your knife while you’re out there. A dive knife can literally save your life while you’re spearfishing, so don’t go for the cheapest option, and get one that will be there for you when you need it. 

As always, if you have any questions about spearfishing, don’t hesitate to leave a message. I’d love to help someone get geared out.

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