One Rep Max Calculator
Estimate your one-rep max (1RM) from the weight and reps you can currently lift, using multiple proven formulas.
Estimated 1RM
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Epley Formula
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Brzycki Formula
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Lombardi Formula
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Mayhew Formula
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Training Percentages
Enter weight and reps above to see training percentages.
How to Use the One Rep Max Calculator
- Choose your unit system: Select Metric (kg) or Imperial (lb).
- Enter the weight lifted: Type the weight you used for your set.
- Enter reps completed: Type the number of reps you completed with good form.
- View your results: Your estimated 1RM from multiple formulas and a training percentage table appear instantly.
1RM Formulas
The following formulas estimate your one-rep max from a submaximal lift:
- Epley: 1RM = weight x (1 + reps / 30)
- Brzycki: 1RM = weight x (36 / (37 - reps))
- Lombardi: 1RM = weight x reps0.10
- Mayhew: 1RM = (100 x weight) / (52.2 + 41.9 x e-0.055 x reps)
These formulas are most accurate for 1-10 reps. Accuracy decreases at higher rep ranges.
Frequently Asked Questions
Which formula is the most accurate?
The Epley and Brzycki formulas are the most widely used and are generally considered the most reliable for rep ranges of 1-10. Results tend to converge at lower rep counts. The average of multiple formulas provides the best estimate.
How should I use the training percentages?
Training percentages help you plan your workouts. For strength training, work in the 80-95% range (1-5 reps). For hypertrophy (muscle growth), use 65-80% (6-12 reps). For endurance, use 50-65% (15+ reps). Adjust based on your program and how you feel.
Should I actually test my one rep max?
Testing a true 1RM can be risky, especially for beginners. Using a calculator with a 3-5 rep max is safer and nearly as accurate. If you do test, always use a spotter, warm up thoroughly, and build up gradually. Most training programs do not require actual 1RM testing.