What the tool does, how to run it, and what to expect from the result.
The Epley formula estimates 1RM as weight x (1 + reps/30), the most widely used estimate for sets of about 10 reps or fewer; accuracy drops on higher-rep sets. The percentage chart applies standard %1RM-to-reps pairings used across strength programs (for example, about 85% of 1RM for 6 reps) so you can plan training weights without retesting your max.
A quick way to understand who this helps, what it solves, and where it connects next.
Lifters programming strength training around a percentage of their max.
Estimating a one-rep max from a lighter, safer set instead of testing it directly.
Short answers for the questions people usually have before trying a utility like this.
Yes. It is completely free, with no sign-up and no usage limits.
Reasonably close for sets of 10 reps or fewer performed close to failure; it tends to overestimate on higher-rep sets or sets stopped well short of failure.
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Enter a weight and the reps you got with it to estimate your one-rep max for the lift, plus a training percentage chart.
157.5 lbEstimated one-rep max (lift)
100% = 157.5 lb (~1 rep)
95% = 149.6 lb (~2 reps)
90% = 141.8 lb (~4 reps)
85% = 133.9 lb (~6 reps)
80% = 126.0 lb (~8 reps)
75% = 118.1 lb (~10 reps)
70% = 110.3 lb (~12 reps)
65% = 102.4 lb (~15 reps)
60% = 94.5 lb (~20 reps)
Uses the Epley formula, most accurate for sets of 10 reps or fewer. Treat this as a training estimate, not a number to attempt cold in the gym.