Freediving weight calculator
Ballast sized for your balance depth, your discipline and your lungs, so you free-fall when you should and float when it matters.
Free to use, no account needed. The calculator loads below.
Freediving weighting is a safety calculation
A freediver is weighted to be neutral somewhere between ten and fifteen metres, not at the surface. Above that depth you are positive, and the shallower you get the more positive you become. That is the whole design: the part of the dive where blackout is most likely is the part where the water is pushing you up.
This is why an overweighted freediver is in a different category of danger from an overweighted scuba diver. Nothing in freediving compensates for bad weighting. There is no inflator.
Balance depth, and why it moves with your target
Weighting to ten metres suits recreational depths. As your target gets deeper, the balance depth here scales toward fifteen metres, because a diver balanced shallow is fighting a lot of positive buoyancy on a long ascent from depth, exactly when they have least to spend.
Below your balance depth you free-fall. Above it you swim. Where that transition sits is the single biggest thing your ballast controls, and it is why the number changes when your target does.
Lungs, suit and discipline
Your lungs are the largest compressible volume you carry, and the calculation treats them as such: a full inhale on a trained diver is eight litres of lift at the surface and one litre at seventy metres. FRC and exhale diving start from a fraction of that, and need correspondingly less lead.
Open-cell freediving neoprene is more buoyant than scuba neoprene, roughly a kilo of lift per millimetre for a full suit, and it compresses with depth like everything else. Discipline matters too: no-fins and pool diving want the weight on a neck weight so your legs do not sink and spoil your trim.
Common questions
How much weight do I need for freediving?
Far less than for scuba. A 75 kg freediver in a 5 mm open-cell suit in salt water typically carries around 3 to 4 kg. The exact figure depends on your suit thickness, your lung volume and your target depth.
At what depth should a freediver be neutral?
Around ten metres for recreational depths, scaling toward fifteen as your target gets deeper. Never at the surface: you must be positively buoyant at the top, where blackout risk is highest.
Should I use a belt or a neck weight?
A rubber hip belt keeps a streamlined vertical trim for finned descents. A neck weight puts the load over your lungs and stops your legs sinking, which is what no-fins and pool disciplines want. Deeper dives are often split between the two.
Why is overweighting so dangerous in freediving?
Because you have nothing to correct it with. An overweighted freediver has to work harder on the ascent, arrives at the surface with less oxygen and less margin, and is not being pushed up by the water in the shallows where blackout most often happens.
The rest of it lives in the app
The app logs your freedives with depth, time and surface interval, tracks your progression by discipline, and keeps your weighting alongside the sessions where it worked.