HesapHanem

RPE to Percentage Calculator

Turn RPE and reps into a %1RM estimate for smarter load selection.

How it is calculated

The tool treats RPE as how many reps you had left and then inverts the Epley formula. reps to failure = reps + (10 − RPE) and %1RM = 100 / (1 + reps to failure / 30). RPE is a number from 1 to 10 (half points such as 8.5 are fine) and reps is the number of reps in the set, 1 or more. The result is a percentage with two decimals. It is a formula estimate and not a table lookup, so it is smooth and gives a value for any reps. It runs a little below 100% even for a single at RPE 10 (96.77%), and it becomes less reliable for sets of about 12 reps or more. Anything outside RPE 1 to 10 returns no result.

Worked example

You did a set of 5 reps at RPE 8. Reps left = 10 − 8 = 2, so reps to failure = 5 + 2 = 7. %1RM = 100 / (1 + 7 / 30) = 100 / 1.2333 = 81.08%. Result: 81.08% of your one-rep max. For comparison, 12 reps at the same RPE 8 gives 68.18%, because a longer set at the same effort uses a lighter weight.

Try this example →

Common mistakes

  • Entering the RPE as the target of the next set instead of how the completed set felt. Rate the set after you finish it.
  • Mixing up RPE with reps in reserve. RPE 8 means about 2 reps left, so do not enter 2 in the RPE field.
  • Calling a set RPE 10 when you only had a hard-feeling set with reps left. An RPE that is too high will make the percentage too high.
  • Using the percentage with a one-rep max that is out of date or only estimated. The percentage is only as useful as the 1RM you multiply it by.
  • Relying on the output for high-rep sets. Above about 12 reps the Epley relationship is a rough approximation and fatigue plays a larger part.

Sources

About this calculator

Rate of Perceived Exertion (RPE), in its strength-training form (the Borg-derived 1-10 scale popularized by Mike Tuchscherer’s RTS system), rates how hard a set felt relative to failure, and each RPE-and-rep-count combination maps to an estimated percentage of your one-rep max: the reps you did plus the reps you had left in reserve (10 minus RPE) give the total you could have done to failure, which the Epley formula converts into a %1RM. An RPE of 8 at 5 reps, for example, corresponds to a materially different %1RM than an RPE of 8 at 12 reps.

Powerlifters and strength athletes use RPE-to-percentage conversion to program training loads without needing a current 1RM test — since RPE is self-reported effort, it naturally adjusts for daily fluctuations in strength from sleep, stress and fatigue in a way a fixed percentage-of-1RM program cannot, while the conversion still lets a coach translate a felt effort into a concrete load recommendation for programming and load selection.

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