There exists no equation as several variables would be factored in to the equation.
However, if your goal was to increase your squat and you remained plateaued for a year, you were doing something wrong.--(Given your stats) Obviously at some point you may reach a max, but that is not your issue given what info you gave.
Small incremental increases as well as periodization is critical once you get into bigger weights. You can't consistantly go heavier and you have to make those steps smaller. Add a washer. Add a lb. Add a 2.5. Add a rep.........
The old story of the guy going out every day and picking up the calf and carrying it around has merit. By the day the calf grew little, but over the year the progress was obvious.