Free 1RM Calculator - Calculate Your Maximum Lift
Calculate your 1RM (one rep max) for weightlifting exercises based on your current performance.
Formula & Methodology
The One Rep Max Calculator estimates the heaviest weight you could lift once from a weight you lifted for several reps. The Epley formula multiplies the weight by (1 + reps/30), while the Brzycki formula uses 36/(37 minus reps); both are established strength-training estimates, and your true 1RM usually falls between them.
- 1RM = Weight × (1 + Reps / 30) (Epley)
- 1RM = Weight × 36 / (37 − Reps) (Brzycki)
Worked Example
Using the One Rep Max Calculator: apply the formula above to your input values. For instance, 1RM = Weight × (1 + Reps / 30) (Epley), then 1RM = Weight × 36 / (37 − Reps) (Brzycki). The tool performs each step instantly and shows the result.
Frequently Asked Questions
What is a one-rep max?
It is the most weight you can lift for a single repetition of an exercise, a key benchmark of strength.
How is 1RM estimated without maxing out?
Formulas like Epley or Brzycki estimate it from the weight and reps you can do, avoiding the injury risk of a true max attempt.
How do I use 1RM for training?
Most programs prescribe a percentage of your 1RM for sets, so knowing it helps you pick appropriate working weights.