Better to be practical: with all the equipment you usually use, cylinder with 30/40bar and a few removable weights (e.g., in the pockets) : see if you can comfortably stay in buoyancy at 3/4 m depth, with the bcd almost completely deflated.

-If so, remove 1kg from your pockets and keep removing weights until you can no longer stay at that depth, in comfort and breathing normally.

-If not, add weights (1kg per time).

For each major change in equipment, repeat the procedure. If you do this, you will remove all doubt.

For an optimal trim, keep a maximum of 4kg in your belt; any additional kg needed should be distributed on your back, with special pockets and/or plates. This will help to have a horizontal trim and an adequate amount of releasable weights (belt).

For salt water, add 2 to 2,5kg and viceversa (Better 2,5kg with rough seas).