One-Rep Max Calculator (Brzycki / Epley / Lombardi)

1RM from a sub-max set using Brzycki, Epley, and Lombardi formulas — three estimates side by side.

Inputs

Result

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How to use this calculator

  • Pick a weight you can do for 3-8 reps with good form.
  • Enter weight + unit + actual reps.
  • Use the average for programming sets at % of 1RM.

About this calculator

1RM (one-rep maximum) is the heaviest weight you can lift once for a given exercise. Three classic prediction formulas: Brzycki tends low at high reps, Epley tends high, Lombardi is the most stable across rep ranges. All three converge below 5 reps; above 8-10 reps they diverge by 5-15%. Use the average for programming. Don't test true 1RM more than every 4-8 weeks — it's neurally taxing and injury-prone for non-elite lifters. Most coaches program off estimated 1RM, not tested.

Frequently asked

Which formula should I trust?+
For 3-5 reps: all three converge. For 6-10: average them. Above 10 reps: estimates are unreliable — drop weight and retest at 5-8 reps.
Why the difference?+
Each formula was fit to a different population. Brzycki to powerlifters, Epley to general lifters, Lombardi to bodybuilders. Your strength curve fits one better.
How accurate?+
Within 5% if reps ≤ 6 and form is consistent. Goes to 15%+ at 10+ reps because of muscular endurance variability.
Should I actually test 1RM?+
Powerlifters competing: yes, on schedule. Strength training generally: no — predicted is enough and safer.
Bench vs. squat formula?+
Same formulas, but squat 1RM tends to predict slightly higher than bench because of more muscle mass involvement and rebound at the bottom.

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Estimate your 1RM from any rep set using Epley, Brzycki & Lombardi formulas — plus a strength % chart.