One-Rep Max (1RM) Calculator
One-Rep Max (1RM) Calculator
One-Rep Max (1RM) is the maximum amount of weight you can lift for a single repetition of an exercise, commonly used to set training percentages (e.g., "work at 80% of 1RM"). Testing a true 1RM directly carries injury risk, so most lifters estimate it from a set of multiple reps at a lighter, safer weight.
The Epley formula, one of the most widely used estimation methods, extrapolates your 1RM from the weight and rep count of a recent set — most accurate for sets of 10 reps or fewer, since higher-rep estimates become less reliable.
- Epley Formula: Estimates 1RM as weight × (1 + reps/30) — simple, widely used, and reasonably accurate for sets under 10 reps.
- Safer Than Direct Testing: Avoids the injury risk of attempting a true maximal single lift.
- Basis for Training Percentages: Programs often prescribe work at specific 1RM percentages (e.g., 70%, 80%, 90%) for strength or hypertrophy phases.
How accurate is the Epley formula?
It is most accurate for sets of 1-10 reps performed close to failure. Estimates from very high-rep sets (15+) tend to be less reliable.
Should I actually attempt my calculated 1RM?
Not necessarily — the estimate is most useful for calculating training percentages. Attempting a true maximal lift should only be done with proper form, warm-up, and ideally a spotter.
One-Rep Max (1RM) Calculator
One-Rep Max (1RM) is the maximum amount of weight you can lift for a single repetition of an exercise, commonly used to set training percentages (e.g., "work at 80% of 1RM"). Testing a true 1RM directly carries injury risk, so most lifters estimate it from a set of multiple reps at a lighter, safer weight.
The Epley formula, one of the most widely used estimation methods, extrapolates your 1RM from the weight and rep count of a recent set — most accurate for sets of 10 reps or fewer, since higher-rep estimates become less reliable.
- Epley Formula: Estimates 1RM as weight × (1 + reps/30) — simple, widely used, and reasonably accurate for sets under 10 reps.
- Safer Than Direct Testing: Avoids the injury risk of attempting a true maximal single lift.
- Basis for Training Percentages: Programs often prescribe work at specific 1RM percentages (e.g., 70%, 80%, 90%) for strength or hypertrophy phases.
How accurate is the Epley formula?
It is most accurate for sets of 1-10 reps performed close to failure. Estimates from very high-rep sets (15+) tend to be less reliable.
Should I actually attempt my calculated 1RM?
Not necessarily — the estimate is most useful for calculating training percentages. Attempting a true maximal lift should only be done with proper form, warm-up, and ideally a spotter.