Enter the amount of weight you lifted, and the number of times you lifted it (reps). This formula is accurate for 1 to 10 reps. It will calculate the approximate maximum amount of weight you should be able to lift for 1 to 10 reps, and will also give you percentages of your one rep max which are used by a number of exercise routines.
All values are rounded to the value you specify. If your plates allow you to do 5 pound increments, and you specify 5, it will round to the closest value you can set on your bar.