One rep max calculator
Estimates your one rep max from a set taken close to failure. Instead of a single equation it shows five — the spread between them tells you how wide the estimate really is.
Result
Fill in the fields and the result appears here.
How it is calculated
1RM prediction equations fit a curve to the relationship between load and reps. They all work the same way: as reps go up, the load you can handle drops in a predictable pattern.
The five equations disagree on the same input, sometimes by as much as 5%. That is why no single "correct" number is shown here — the average appears next to the lowest and highest estimate.
These equations were derived in the 1-10 rep range and behave reasonably there. Past 10 reps the estimate degrades quickly, because what limits a 15-rep set is muscular endurance more than maximal strength. The set also has to be taken close to failure: a set with three reps left in reserve will understate your 1RM.
An estimate does not replace testing. The reason to use one anyway is the cost of a true maximal attempt — fatigue and technical breakdown. For programming, an estimate is usually enough.
Sources
- Epley B. (1985). Poundage Chart. Boyd Epley Workout, Body Enterprises.
- Brzycki M. (1993). Strength testing: predicting a one-rep max from reps-to-fatigue. JOPERD 64(1): 88-90.
- Lombardi V.P. (1989). Beginning Weight Training. Wm. C. Brown.
- LeSuer D.A. ve ark. (1997). The accuracy of prediction equations for estimating 1-RM performance in the bench press, squat, and deadlift. J Strength Cond Res 11(4): 211-213.
You have the number — now comes the decision
Comparing these numbers against weekly data and revising with a stated reason is the actual work. That is how online coaching runs here.