Typically it’s one or two more than you think you’re capable of.
I fear that a good portion of people do not maximize the efficiency of their time spent exercising when they go into the gym without a plan.
Whatever you’re doing, whether it’s beginner push-ups supported on your knees, or heavy squats with a loaded barbell, you must push yourself a little bit past what you think your natural limit is.
That’s the whole point.
You should be constantly increasing your fitness, little by little, in this manner.
Now, I know that that last extra rep or two can be a real battle. It can burn. It can hurt. You have to really psych yourself up and be absolutely determined to go for it, in order to make it.
But it’s that last extra rep or two that deliver the results.