1RM Calculator
Estimate your One Rep Max
1RM Calculator
Estimate your One Rep Max
How it works
Your one-rep max (1RM) is the heaviest weight you can lift for a single repetition of an exercise. Knowing it lets you program training as a percentage of your max instead of guessing.
Rather than testing a true max (which is fatiguing and risky), this calculator estimates your 1RM from a set you've already done using the Brzycki formula: 1RM = weight / (1.0278 − 0.0278 × reps). It is most accurate for sets of 1–10 reps.
The percentage table shows the load for 70–95% of your estimated max — useful for picking working weights: strength work typically lives at 85–95%, hypertrophy around 70–80%.
Frequently Asked Questions
How is 1RM calculated?
This calculator uses the Brzycki formula: 1RM = weight / (1.0278 − 0.0278 × reps). It estimates the maximum weight you could lift for a single repetition from a multi-rep set.
How many reps should I use for the best estimate?
Estimates are most accurate for sets of 1–10 reps. The further past 10 reps you go, the less reliable the estimate becomes.
Calculations are estimates for educational purposes. Consult a professional before starting any new diet or exercise program.