One-Rep Max (Epley) Calculator
The one-rep maximum (1RM) is the heaviest weight you can lift for a single repetition with correct technique. Testing your true 1RM carries injury risk, so strength coaches use predictive formulas to estimate it from submaximal sets. The Epley formula, developed by Boyd Epley at the University of Nebraska in 1985, is one of the most widely cited: 1RM = weight x (1 + reps / 30). Enter the weight you lifted and the number of reps you completed, and the calculator will estimate your one-rep max along with percentage-based training loads commonly used in periodized strength programs.
Epley 1RM formula
1RM = weight × (1 + reps / 30)
Where weight is the load lifted and reps is the number of repetitions completed in the set. The formula assumes a linear relationship between load and rep capacity. For a single rep (reps = 1), the formula returns weight x (1 + 1/30) = weight x 1.0333, which slightly overestimates the true 1RM. The formula is most accurate in the 2 to 10 rep range.
Using your 1RM for training
- Strength (1 to 5 reps): Use 85 to 100 percent of 1RM.
- Hypertrophy (6 to 12 reps): Use 65 to 80 percent of 1RM.
- Muscular endurance (12 or more reps): Use below 65 percent of 1RM.
- Re-test your estimated 1RM every 4 to 8 weeks as strength improves.
- For safety, always use a spotter or safety equipment when lifting near your 1RM.
One-rep max calculator: frequently asked questions
What is the Epley formula for one-rep max?
The Epley formula estimates your one-rep max as: 1RM = weight x (1 + reps / 30). It was developed by Boyd Epley and published in 1985. It works best when you use a rep count between 2 and 10.
How accurate is the Epley 1RM estimate?
The Epley formula is one of the most widely validated predictive equations in strength research. Accuracy is highest at lower rep counts (2 to 6 reps). At 10 or more reps, fatigue and technique factors reduce accuracy, so treat the result as an estimate rather than an absolute value.
Can I use this calculator for any lift?
Yes. The Epley formula is lift-agnostic and can be applied to the squat, bench press, deadlift, overhead press, or any single-joint movement. Results will be most reliable for compound barbell lifts tested in a consistent manner.
What rep range gives the best estimate?
Research consistently shows that predictions are most accurate when using a weight you can lift for 2 to 6 repetitions. Using a set performed to failure at a moderate weight (around 5 reps) tends to yield the best 1RM estimate with the Epley equation.
How do I use my estimated 1RM for programming?
Strength coaches commonly use 1RM percentages to set training loads. For example, a hypertrophy block might use 65 to 75 percent of 1RM for 8 to 12 reps, while a strength block might use 80 to 90 percent for 3 to 5 reps. The NSCA Essentials of Strength Training and Conditioning provides evidence-based load and rep recommendations.
Official sources
- Epley, B. (1985). Poundage chart. In Boyd Epley Workout. Lincoln, NE: Body Enterprises. Cited in: NSCA: Muscular Strength Testing and 1RM Prediction.
- National Strength and Conditioning Association (NSCA): nsca.com.
- Brzycki, M. (1993). Strength testing: predicting a one-rep max from reps-to-fatigue. Journal of Physical Education, Recreation and Dance, 64(1), 88-90.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.