One Rep Max Calculator
Estimate your one-rep max without maxing out. Enter the weight you lifted and how many reps you managed, and this free 1RM calculator shows estimates from both the Epley and Brzycki formulas, plus their average. You also get a percentage table so you can plan warm-ups and working sets anywhere from 70% to 100% of your max.
Frequently Asked Questions
What is a one-rep max (1RM)?
Your one-rep max is the heaviest weight you can lift for a single clean repetition of an exercise. It is the standard baseline for strength training programs, which usually prescribe working sets as a percentage of your 1RM.
Which formula is more accurate: Epley or Brzycki?
Both are widely used and neither is perfect. Epley (weight × (1 + reps/30)) tends to run slightly generous at higher rep counts, while Brzycki (weight × 36/(37 − reps)) is a touch more conservative. Showing both plus their average gives you a practical middle ground.
How many reps should I enter for the best estimate?
Use a recent near-maximal set of 1–10 reps — the fewer the reps, the more accurate the estimate. Accuracy drops noticeably above about 10 reps, so a heavy triple or set of five beats a light set of twenty.
Does it matter whether I use kg or lb?
No. Both formulas are unit-agnostic: enter kilograms and the result is in kilograms, enter pounds and the result is in pounds.