Strength · Free tool

RPE calculator

RPE calculator translates completed sets, repetitions, and rating of perceived exertion into reps-in-reserve load projections for autoregulation.

A steel spring compresses beneath a smooth weight plate, suggesting perceived effort.

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Your estimate

Illustrative target working weight

100 kg

Estimated repetitions in reserve
2
Heuristic estimated 1RM
123.33 kg
Target repetitions in reserve
2

Heuristic: RIR = 10 − RPE, then Epley uses completed reps + RIR. This extension is not a validated RTS percentage table or an individualized readiness assessment.

How to use this RPE calculator

  1. Enter the load and repetitions from a completed set.
  2. Enter your estimated set RPE, from 6 to 10.
  3. Choose target repetitions and target RPE, then select Calculate to compare the illustrative load and assumed reps in reserve.

The formula and method

This tool uses a resistance-training repetitions-in-reserve assumption: RIR = 10 − RPE. Under that convention, RPE 8 corresponds to an estimate of two repetitions remaining.

Effective repetitions = completed repetitions + RIR. The heuristic estimated 1RM uses the Epley factor 1 + effective repetitions ÷ 30, except an effective single repetition uses a factor of 1. Target load = heuristic estimated 1RM ÷ the corresponding target factor.

The form accepts RPE 6–10 and one to ten completed or target repetitions. Either combination must have effective repetitions of 12 or fewer. This extension of Epley is an explicitly chosen heuristic, not an official RTS percentage chart or a validated individual load prescription.

Worked example

If you complete 5 reps with 100 kg at RPE 8 (2 reps in reserve), your effective reps equal 5 + 2 = 7 reps. Estimated 1RM = 100 × (1 + 7/30) = 123.3 kg. To find your target load for 5 reps at RPE 9 (1 RIR, effective 6 reps): Target Weight = 123.3 / (1 + 6/30) = 102.8 kg.

Understanding the estimate

  • RPE is subjective, and an inaccurate RIR estimate directly affects the result.
  • The extension assumes additional repetitions follow the chosen Epley relationship; that is not guaranteed.
  • The displayed load does not assess readiness, technique or a suitable next training attempt.

Frequently asked questions

Is this the Borg 6–20 scale?

No. This tool uses a resistance-training RIR-based convention, with inputs restricted to RPE 6–10.

Can I use half points?

Yes. The input supports half points. The arithmetic treats RPE 8.5 as an estimated 1.5 repetitions in reserve.

Why does the same target give the same load?

When completed and target repetitions and RPE match, the same factor appears in the numerator and denominator, returning the entered load.

Sources and further reading