One-Rep Max Calculator
Estimating a max without having to attempt one.
Reading your result
Fill in every field and the steps will be spelled out here.
How it is calculated
Testing a true max carries real risk. Maximal attempts injure people and cost days of recovery, so the standard approach is to infer the number from a safer set — which is what the Epley formula, used here, does.
Accuracy degrades as reps rise. Past ten, muscular endurance starts contributing and the estimate flatters you. A set of roughly five is the most reliable input; a fifteen-rep set produces a number worth ignoring.
The percentage table is for programming. Strength work generally sits above 85% for low reps and hypertrophy around 70–80% for moderate reps — though it varies by lift, and squats behave differently from bench presses at the same percentage.
Frequently asked questions
There are several formulas — which one?
Epley, Brzycki and Lombardi all differ slightly, converging at low reps and diverging at high ones. Picking one and staying with it matters more than which one, since you are usually tracking change.
Should I attempt the estimated max?
Not recommended. It is a programming reference, not a target. Maximal attempts without a spotter and proper preparation are how people get hurt.
Does it vary by exercise?
Yes. Lower-body lifts tend to allow more reps at a given percentage, so the table reads conservative for them and fits upper-body lifts more closely.
A statistical estimate that varies considerably with lift, training history and condition. Maximal attempts carry injury risk.