ARC guide
RPE vs RIR
RPE 10 is about 0 reps in reserve. The scale is a communication tool, not a precise instrument.
Direct answer
In ARC’s education table, RPE 10 ≈ 0 RIR, 9 ≈ 1, 8 ≈ 2, 7 ≈ 3. RIR is “reps you could still do.” RPE is how hard the set felt on a 10-point scale. They are useful for logging. They are not perfectly precise.
Key takeaway
Use RPE/RIR to keep hard sets honest. Do not use them as a second 1RM formula.
How ARC treats optional RPE
The 1RM calculator can record an RPE so you remember how hard the set was. The math still uses the weight and reps. A set at RPE 8 is not converted into a different 1RM behind the scenes.
People mis-rate RPE, especially early on. That is expected. The point is a shared language for “this was a top set” versus “this had room.”
Example
You squat 275 × 4 and could have done one more clean rep. That is about RPE 9 / 1 RIR. The 1RM estimate still comes from 275 and 4.
Common mistake
Calling every hard set RPE 10. If you never leave a rep in reserve on paper, the scale stops meaning anything.
Use the ARC tool
Run the numbers instead of guessing from the article alone.
How ARC treats this
- The RPE–RIR pairing above is the mapping ARC displays for education. It is approximate.