Start with a set you know
Enter a recent working set: the load, completed reps, and your estimate of how many clean reps were left. Then choose the reps and effort you want to estimate. Keep the exercise, range of motion, and equipment consistent.
RPE means rating of perceived exertion. This calculator uses the lifting-specific scale tied to reps in reserve (RIR). It is different from the 6–20 Borg scale sometimes used for aerobic exercise.
RPE and reps in reserve
| RPE | Estimated reps left | How to read it |
|---|---|---|
| 10 | 0 | No further clean rep was possible. |
| 9 | 1 | About one more rep. |
| 8 | 2 | About two more reps. |
| 7 | 3 | About three more reps. |
| 6 | 4 or more | Comfortably submaximal; harder to estimate precisely. |
A half-point is an intermediate judgment. The tool treats RPE 8.5 as 1.5 estimated reps left and RPE 6 as four. Those are modeling conventions, not something a lifter can measure to a fraction of a repetition.
What this calculator estimates
We combine estimated reps left with the Epley repetition formula. This is a transparent approximation; it is not a proprietary RPE percentage table and has not been individually calibrated to you.
Effective reps = completed reps + (10 − RPE)
Estimated 1RM = load × (1 + effective reps ÷ 30)
Target load = estimated 1RM ÷ (1 + target effective reps ÷ 30)
A single rep at RPE 10 is treated as the entered max, without adding the formula’s usual uplift. Inputs are limited to 1–10 completed reps and RPE 6–10. Even within that range, exercise differences, fatigue, and inaccurate RIR estimates can change the result.
100 kg × 5 at RPE 8
Five completed reps with two estimated reps left gives seven effective reps. The calculation is 100 × (1 + 7 ÷ 30), or an estimated 123.33 kg 1RM.
For three reps at RPE 8, the target has five effective reps. Dividing 123.33 by (1 + 5 ÷ 30) gives approximately 105.71 kg. That is an estimate to interpret and round to available equipment, not an instruction to load that exact weight.
Common questions
Should I test the estimated max?
You do not need to attempt a max to use this tool. Treat it as context for comparable working sets. An estimate is not proof that a heavier attempt will be successful.
Why is my result different from another RPE calculator?
Some tools use empirical percentage tables or other prediction equations. This one uses the explained Epley-plus-RIR approximation. Different methods can disagree, especially at higher repetitions.
Can I compare different exercises?
Use the estimate within the same exercise. A squat estimate does not predict a leg-press load, and changing technique or equipment can make comparisons misleading.
Sources & method
Written by the Brolic team. These references explain the evidence and assumptions; this page does not replace individualized professional advice.
- Zourdos et al. — Resistance training-specific RPE scale (2016) — Repetitions in reserve and perceived effort.
- LeSuer et al. — Accuracy of 1RM prediction equations (1997) — Comparison of repetition-based estimates, including Epley.
- Zourdos et al. — Accuracy of repetitions-in-reserve estimates (2021) — Effort judgments have limitations.