How to use the three effort scale converter
There is more than one way to put a number on exercise effort. This page shows that Borg 6-20, RIR-based RPE 0-10 and Borg CR10 are separate scales, and converts only the pairs that genuinely convert. Pick a scale, enter a value, and the screen states what converts and what does not.
The only conversion that holds is between RIR and RIR-based RPE, where RPE equals 10 minus RIR. Borg 6-20 was designed so that a value tracks roughly one tenth of heart rate in a healthy 20-year-old, so multiplying by 10 gives an approximate figure in beats per minute; entering your age shows how far you sit from that reference age. Borg CR10 rates localised sensations such as breathlessness or pain and carries no heart rate link (current as of October 2026).
No table converting RPE or RIR into a share of 1RM is offered. The whole point of the work that proposed RIR-based RPE is that the number of reps possible at the same share of 1RM varies widely between individuals. No recognised formula links Borg 6-20 to the other two scales either, so this page does not invent one.
Frequently asked questions
There is no recognised formula to map them. Borg 6-20 rates whole-body exercise intensity, while RIR-based RPE is defined by the reps left in reserve on a resistance set, which makes them entirely different scales.
This page does not build that table. The reason RIR-based RPE was proposed in the first place is that the number of reps possible at the same share of 1RM differs widely from person to person.
Only the numeric range matches. CR10 rates the strength of a localised sensation such as breathlessness or pain, while RIR-based RPE reports the reps you left in reserve on a set.