When you use {fraction} PSB, the required odds are simple to calculate.

{numerator} / {2*numerator + denominator}
or, I find it easier to think of it this way

{numerator} / {numerator + numerator + denominator}

1/2 PSB is 1/(1 + 1 + 2) = 1/4 = 25%

3/4 PSB is 3/(3 + 3 + 4) = 3/10 = 30%


Note, it's the same equation. I haven't changed anything mathematically except to think of the numbers as a fraction of the pot size.
What that does is normalize our math to a standard, but that's no small thing.
Being able to simplify this one equation that we calculate many times per hand is a very big deal.