One-Rep Max Calculator
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Estimated one-rep max
Epley: 1RM = w × (1 + r/30). Brzycki: 1RM = w × 36/(37 − r). Here w is weight and r is repetitions. Both return w for r = 1. Source: Brzycki (1993).
Estimated load as a percentage of 1RM
These percentages invert the same formulas: Epley = 100/(1 + r/30); Brzycki = 100 × (37 − r)/36. One rep is 100% for both. The table works with kg and lb.
| Reps | Epley | Brzycki |
|---|
Treat these as estimates. Fatigue, exercise choice, technique and training experience affect how much you can lift.
For general information only; not medical advice.
How to use this tool
Choose kg or lb and enter the weight and number of repetitions in one hard set. Select Estimate one-rep max to compare both formulas.
Frequently asked questions
What is a one-rep max?
It is the most weight you can lift once with good form for a particular exercise. This calculator estimates that weight from a set of repetitions.
Why are there two answers?
Epley and Brzycki use different equations, so their estimates can differ. Neither guarantees a lift you can perform. The closer the set is to your limit, the more useful the estimate may be.
How many reps should I enter?
Enter a whole number from 1 to 12. Estimates get worse past about 10 reps. If you enter one rep, both formulas return the weight you lifted.
What does the percentage table mean?
Each row estimates the load for that many reps as a percentage of one-rep max, using the inverse of each formula. It is a rough guide, not a training prescription.