One-rep max calculator (1RM)
Estimate your one-rep max from a set of 1–12 reps, without testing it. Uses the Epley and Brzycki formulas, with a percentage chart for your working sets.
How it works
Your max is estimated from a set you’ve already done: the weight and how many reps you managed with good form. Two common formulas are [1]:
- Epley: weight × (1 + reps ÷ 30)
- Brzycki: weight × 36 ÷ (37 − reps)
The calculator shows both and uses their average, rounded to the nearest 5 lb or 2.5 kg. It accepts sets of up to 12 reps: longer sets depend more on endurance than strength, so they predict a max less well.
How accurate is it?
In a study of 67 beginners in a weight training class, estimates from sets to failure correlated very closely with their tested maxes (r > 0.95). Most formulas were a little off on average for the bench press and squat, and all of them underestimated the deadlift [1].
A set you stopped well short of failure will underestimate your max. That’s fine: an estimate on the low side is safer to plan with.
Using the chart
The chart shows the weight for each percentage of your estimated max and roughly how many reps you could do with it (from the Epley formula, run backwards). Use it to pick working weights for a program written in percentages.
You don’t need a max to follow the programs on this site. They use rep ranges: when you hit the top of the range on every set, add weight. See the beginner program and the strength goal.
Loading the bar
Once you know the weight, the barbell plate calculator shows which plates go on each side.
Questions
How accurate is a one-rep max calculator?
Good enough for planning. In a study of beginners, estimates from a set to failure lined up closely with real maxes on the bench press and squat, but underestimated the deadlift. The closer your set is to failure, and the fewer the reps, the better the estimate.
Should beginners test their one-rep max?
There’s no need. Maxing out adds risk and needs a spotter or safeties, and the programs on this site use rep ranges instead of percentages. An estimate from a normal set tells you what you need to know.
Which formula is best, Epley or Brzycki?
They agree closely at low reps and drift apart as reps go up. This calculator averages them. For the most useful number, use a set of 3–8 reps taken close to failure with good form.
How often should I check my one-rep max?
Every few weeks is plenty. Your working weights going up is the real sign of progress.
Sources
- [1]LeSuer et al., The Accuracy of Prediction Equations for Estimating 1-RM Performance in the Bench Press, Squat, and Deadlift, Journal of Strength and Conditioning Research (1997). https://journals.lww.com/nsca-jscr/abstract/1997/11000/the_accuracy_of_prediction_equations_for.1.aspx