1RM Calculator is a browser tool for estimating a lifter's one-repetition maximum from a completed set. It supports weight and rep inputs, formula comparisons, and percentage tables for planning bench press, squat, deadlift, and other strength sessions.
External tool opens in a new tab.
What is this tool?
Estimate your one-rep max from weight and repetitions, compare common formulas, and review training percentages.
Best for
Lifters and coaches who want a quick one-rep max estimate and percentage guide before planning a workout.
Pricing note
The calculator is free to use. Results are estimates rather than medical or coaching advice, and actual performance depends on technique, fatigue, equipment, and training context.
Key features
Use cases
Estimate a 1RM after a submaximal set.
Plan working weights for a strength session.
Compare formula results before recording a training target.
Pros
Cons
How to use
Enter the weight used and the number of completed repetitions.
Review the estimated one-rep max and compare the available formulas.
Use the percentage table to choose a training weight, then adjust for your actual readiness.
Record the result and retest after a meaningful training cycle.
FAQ
What is a 1RM?
A one-rep max is the heaviest load you can lift once with controlled technique for a given exercise.
How does the calculator estimate 1RM?
It applies established repetition and load formulas to the weight and reps you enter, then presents an estimate and percentage targets.
Can I use it for squat, bench press, and deadlift?
Yes. Use the estimate as a planning reference for common barbell lifts and compare it with your current training context.
Is an estimated 1RM exact?
No. Formula results are approximations; fatigue, technique, range of motion, and equipment can change your real maximum.
Is this a substitute for a coach?
No. It is a calculation aid and does not replace qualified instruction or safe strength-training decisions.
