Testing a true one-rep max on a heavy lift carries real injury risk, so most lifters estimate it instead from a lighter set taken close to failure. This calculator uses the Epley formula, one of the most widely used estimation methods in strength training.
| % of 1RM | Approx. weight | Typical reps |
|---|
Use this instead of actually testing a true one-rep max, which carries real injury risk without a spotter and proper technique. It's most useful for programming training percentages — knowing what weight corresponds to 80% or 70% of your max lets you follow a structured strength program without needing to retest your max every few weeks.
The Epley formula is: one-rep max = weight lifted x (1 + reps performed / 30). It's most accurate for sets of roughly 10 reps or fewer performed close to failure; estimates get less reliable for higher-rep sets.
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