RPE vs RIR: how hard was that set?
RIR is how many more clean reps you think you could have done. On the RIR based lifting scale, RPE expresses the same estimate as effort: 2 RIR is about RPE 8, 1 RIR is about RPE 9, and 0 RIR is RPE 10.
RPE stands for rating of perceived exertion; RIR stands for repetitions in reserve. Both are estimates you make after a set. They add context to the load and reps in your training log, especially when the same weight feels different on another day.
The scale in one breath
On this version of the scale, RPE 10 means about zero reps left; RPE 9 means about one; RPE 8 means about two. Half steps describe the space between. The original RIR based RPE study uses this mapping. Other RPE scales exist, so write down which one your program uses.
| RPE | Estimated RIR | Meaning |
|---|---|---|
| 10 | 0 | No more clean reps |
| 9 | 1 | About one more clean rep |
| 8 | 2 | About two more clean reps |
| 7 | 3 | About three more clean reps |
This conversion is an estimate for the RIR based scale. It is less precise when a set is far from failure or the exercise is unfamiliar.
Example: you complete 6 bench reps at 70 kg and think you could have done 2 more with acceptable technique. Log 70 kg × 6 @ RPE 8, or 70 kg × 6 @ 2 RIR.
Move the effort dial
Drag the dial after a hard set. The graph shows perceived effort and estimated reserve on the same scale. It is a translation aid, not a sensor measurement.
Effort dial
InteractiveThe RPE–RIR mapping is approximate. It becomes less informative far from failure and can vary by lift and experience.
Where the number gets shaky
RIR is a prediction. You never actually test the remaining reps unless you continue toward failure. One study across four exercises found that estimates around 2 RIR were more accurate at heavy loads, while lighter loads made larger underestimates more likely. Another study of 141 participants found that prediction of reps to failure was imperfect but improved with training experience.
That is not a reason to throw RPE away. It is a reason to treat it as a calibrated estimate. A quick note such as “RPE 8, final rep slower than usual” can be more useful than pretending the exact number is certain.
How to use it in a log
- Write the rating immediately after the set, before the feeling fades.
- Judge reps you could have completed with the same technique and range of motion.
- Compare the same lift and rep range over time.
- Recalibrate when you train a new exercise or return after a break.
If a planned RPE 8 set feels like RPE 10 today, pause and review the next set. It may be a hard day, a too-heavy load, or simply an inaccurate estimate. Load and bar speed can add context, but neither replaces your judgment.
Evidence and further reading
Effort belongs next to the numbers.
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