The information below is based on William Ng's 5 Cuts to a "Perfect" Cross-Cut Sled discussion on YouTube. The units (inches, mm) don't matter, as long as all measurements are in the same units.
If result is positive, adjust the fence backward. If result is negative, adjust the fence forward.
08/03/2020 - Thanks to Johnny Brooke of Crafted Workshop for mentioning and linking to the above calculator on his "Table Saw CROSSCUT SLED w/ Stop Block & DUST COLLECTION // How To Make" episode at the 9:30 mark.