To use this calculator, please plug in a recent 1-rep-max (1RM) effort, or ‘rep personal record (PR)’ from training (i.e. you crushed 8 reps of back squat at 200 lbs. for 10 reps at a 10/10 effort). You will plug in the total reps performed, and weight lifted (in lbs or kb) below. It will then estimate your 1RM from this data and chart your potential lifting performance below.​


The calculator will be most accurate for weights that are plugged in for sets taken closer to failure (0 reps left). It will also be more accurate at estimating potential performance the closer the data plugged in is to the goal rep range (i.e. 1RM estimation from a PR set of 10 reps will be less accurate than data for a PR set of 3 reps, and vise-versa).


The calculator is also to be used as a general reference, and won’t always perfectly reflect individual variations in performance. RPE/RIR based guidance is also general and based on estimated % of 1RM, but does not take into account individual variation or day-to-day impacts on performance. I recommend using RPE as a long term training tool, and this calculator as a general performance reference or starting point.​​


Not sure how to use RPE (rating of percieved exertion) or RIR (reps in reserve)?
Check out my free resource here on using RPE and RIR in training!​

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Exercise Scientist, ultra runner, lifter, human.