1RM Calculator
Estimate a practical one-rep max from a challenging working set using the Epley strength formula.
Frequently asked questions
Which 1RM formula does this calculator use?
It uses the Epley formula: weight multiplied by one plus repetitions divided by 30.
How many reps are best for estimating 1RM?
Predictions are generally most useful from challenging sets of roughly 1 to 10 repetitions completed with consistent technique.
Is an estimated 1RM safe to use for training?
Use it as a planning estimate. Increase load conservatively and use qualified coaching, spotters, and sound technique when attempting heavy lifts.
Can I use this calculator for any lift?
Yes. The Epley formula works for any compound or isolation lift where you complete a set with consistent technique. Common uses include bench press, squat, deadlift, and overhead press.
What are the limitations of 1RM estimation formulas?
Estimates are less accurate for high-rep sets above 10 reps, for exercises where technique changes under fatigue, and for people new to lifting whose neural adaptations are still developing.