How Much Extra Powder Constitutes +P Loads in these?

I know it is specific to calibers and weights of the bullets...and barrel lengths.

So, with "average barrel lengths" of pistols using these calibers, with these gr cast lead boolits, using WIN231 or near equivalent powders...how many extra (%?) .1, or .01 of powder would I need to add to make +P loads?

.32 acp 75gr..(max load per Lyman 48th is 2.5grs)

380 acp 102gr..........(max per Lyman's Cast Bullet Handbook 4th is 3.1grs)

9x18 Makarov 100gr...( " LCBH 4th is 3.7 )

9mm Luger 124gr.....( " Lyman's 48th is 4.3 )

40 S&W 180gr.........( " LCBH is 5.2)

.45 acp 200gr...........( " " is 6.0)