One Rep Max Calculator
Your one-rep max is the heaviest load you could lift once with good technique. Rather than testing it, you can estimate it from a set you already completed: enter the weight and the reps, and the calculator averages the Epley and Brzycki formulas, then breaks the result into the percentages most programs are written around.
- Accurate
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Estimated one-rep max
114.6 kg
90% of 1RM
103.1 kg
Details
Updates as you typeThe load on the bar for the set you actually completed.
Whole reps taken close to failure. Accuracy drops badly above 12.
Summary
Estimated one-rep max
114.6 kg
- 95% of 1RM
- 108.9 kg
- 90% of 1RM
- 103.1 kg
- 85% of 1RM
- 97.4 kg
- 80% of 1RM
- 91.7 kg
- 70% of 1RM
- 80.2 kg
- This is an estimate from a submaximal set, not a tested max. The two formulas disagree by a few percent, and the spread widens as reps rise.
- The set must have been taken close to failure. Reps left in reserve make the estimate read low.
- Never attempt a true one-rep max without a spotter, a warm-up, and technique you can hold under load.
How this is calculated
- Epley: weight x (1 + reps / 30)
- 116.7 kg
- Brzycki: weight x 36 / (37 - reps)
- 112.5 kg
- Average of the two estimates
- 114.6 kg
Reps
Compare scenarios
See how one change moves the result
- CurrentYour inputs as they stand114.6 kgCurrent
- Weight liftedkg 125143.2 kg
- Reps completed6118.1 kg
For informational purposes only. This is not medical advice — consult a healthcare professional about your health.
Frequently asked questions
How accurate is an estimated one-rep max?
Within a few percent for sets of 1 to 5 reps taken close to failure, and progressively looser above that. The formulas assume an average strength-endurance profile, so lifters who grind out high-rep sets tend to have their max overestimated.
Why does this calculator average two formulas?
Epley is generous at higher reps while Brzycki is conservative there, and they cross over near five reps. Averaging them cancels most of the individual bias and gives a number that sits closer to tested maxes across the usual rep range.
Why is the rep count capped at 12?
The Brzycki denominator of 37 minus reps collapses toward zero as reps climb, and both formulas were fitted on low-rep data. Past about a dozen reps the estimate is dominated by conditioning rather than maximal strength, so a heavier set gives a far better answer.
What are the percentages of my max used for?
Most strength programs prescribe load as a percentage of your one-rep max: roughly 85 to 95 percent for heavy strength work, 70 to 85 percent for hypertrophy volume, and below 70 percent for technique or speed practice.
Should I retest my one-rep max often?
A true max test is fatiguing and carries the most injury risk of anything you do in the gym. Re-estimating from a hard set of three to five reps every few weeks tracks progress just as well with a fraction of the cost.