Calculate your one-rep max with the Epley formula from lifted weight and reps, and find training weights for target percentages or reps.
Safety & accuracy note: Heavy lifting (including attempting a true 1RM) carries injury risk. Use this calculator’s 1RM as an estimate for training/programming—do not attempt a maximal lift without proper technique, warm-up, and appropriate supervision. If you have pain, an injury, a medical condition (including heart/blood pressure concerns), are pregnant, or are new to lifting, consult a clinician and/or a certified coach first. Epley estimates are generally most accurate for lower-rep sets (often up to ~10–12 reps); higher reps can be less reliable.
Epley Formula
The Epley Formula is used to estimate the maximum amount of weight one can lift in a single repetition (1RM) for a given exercise.
Variables:
- 1RM is the one-repetition maximum (lb/kg/stone)
- W is the weight lifted (lb/kg/stone)
- R is the number of repetitions
To estimate the 1RM, multiply the weight lifted by the sum of one and the quotient of the number of repetitions divided by 30. Use the same unit for 1RM and W. For a maximal single (R = 1), this tool uses W directly rather than the algebraic formula above. Plate rounding applies only to displayed loads.
What is a One-Rep Max (1RM)?
A one-rep max (1RM) is the maximum amount of weight that a person can lift for one repetition of a given exercise. It is a standard measure used to assess an individual’s maximum strength and is commonly used by weightlifters, bodybuilders, and athletes. Knowing your 1RM can help you set appropriate weight levels for strength training and track your progress over time.
How to Calculate One-Rep Max (1RM)?
The following steps outline how to calculate the One-Rep Max (1RM) using the Epley Formula.
- First, determine the weight lifted (W) in your preferred unit (lb/kg/stone).
- Next, determine the whole number of repetitions (R) completed to repetition fatigue with consistent technique; this tool accepts 1–30.
- Next, gather the formula from above = 1RM = W * (1 + (R / 30)).
- Finally, calculate the One-Rep Max (1RM) in the same unit as W.
- After inserting the variables and calculating the result, check your answer with the calculator above.
Example Problem :
Use the following variables as an example problem to test your knowledge.
Weight lifted (W) = 200 lbs
Number of repetitions (R) = 5. The unrounded Epley estimate is 200 × (1 + 5/30) ≈ 233.33 lb.
