How to Calculate Weights for Freediving

Updated February 21, 2017

Freediving is diving without the aid of a breathing device. There are many reasons you may want to free dive including: spear fishing, underwater photography, a job removing barnacles from boat hulls or maybe you want to compete in an apnoea competition. Freediving, particularly in saltwater, requires a weight belt to counteract the natural buoyancy of your body and the air in your lungs. Without the extra weight, there is a limit to how deep you will be able to dive. On the other hand, you do not want so much weight that you are unable to surface.

Calculate the formula for the weight required to achieve neutral buoyancy at the depth you desire while freediving by accounting for your body's fat percentage, the capacity of your lungs, the buoyancy of the clothing and equipment you are wearing and the type of water -- fresh or salt. For the average person, fresh water will require weights of about five per cent of your body's to achieve neutral buoyancy at 15 feet. For salt water, add three per cent more. Another method is trial and error.

Put on your diving mask and fins. Check your depth gauge. Make sure it is calibrated correctly. If you are in freshwater, your depth will be three per cent greater than indicated if your gauge is calibrated to read the barometric pressure of saltwater. Three per cent is not a great difference, but accuracy is critical for freediving.

Test your buoyancy in small weight increments. It is safer to achieve neutral buoyancy at a shallower depth and add weight on your second test than sink too quickly and struggle to return to the surface. Do not add more than five pounds at a time when testing for neutral buoyancy.

Add weight, dive, find neutral buoyancy and check your depth gauge. Add weight until you reach a neutral buoyancy of 15 feet. If you cannot reach 15 feet by adding weight, settle for neutral buoyancy at a shallower depth. Depending on what you are wearing, you may reach neutral buoyancy at 15 feet with as little as 1.36 Kilogram or it may require more than 25. If you are an experienced freediver and have a reason to add to the depth of your neutral buoyancy, make sure your partner knows what your farthest depth rate is.


Never, under any conditions, freedive without a partner. A partner is your only safety valve if you get into trouble. In addition, a partner you can trust is a good second conscience whom will assure you make safe decisions. Remember, if you have been freediving for several hours, you may not be aware of your exhaustion level. A partner can keep you thinking clearly.

Things You'll Need

  • Depth gauge
  • Weight belt or vest
  • Weights
  • Diving mask
  • Fins
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