Borg Perceived Exertion Scale Calculator

Borg RPE Scale for Cardiac Rehabilitation

The Borg Rating of Perceived Exertion (RPE) lets you gauge how hard a workout feels when no heart rate monitor is around. The original scale runs from 6–20. That odd range was chosen on purpose: multiply your rating by 10 and you get roughly your heart rate in beats per minute, so RPE 13 lands near 130 bpm. People usually write it as HR ≈ RPE × 10.

There's also a reworked version, the Borg CR-10 (category-ratio), which runs on a 0–10 scale. Clinicians tend to reach for it when assessing breathlessness or programming resistance work. Both forms show up in ACSM and AHA guidance on setting safe exercise intensity for cardiac rehab.

Applications

It comes up across cardiac rehab phases II–IV, with patients on beta-blockers whose heart-rate response is blunted, when there's no wearable to lean on, in pulmonary rehab, and for pacing in chronic disease. For moderate cardiac rehab the target zone usually sits around RPE 11–14 (light to somewhat hard) on the 6–20 scale, or 3–5 on CR-10.

FAQ

Why use RPE instead of heart rate? Beta-blockers and similar cardiac drugs flatten the heart-rate response, so a bpm target can mislead you. Perceived effort doesn't care what medication you're on, which is exactly why RPE holds up.

What is the difference between Borg 6–20 and CR-10? The 6–20 scale tracks heart rate in a roughly linear way. CR-10 is a ratio scale that works better for symptoms like breathlessness or muscular effort, and it pins a verbal description to each level.

Is RPE accurate? Once patients are coached to read the scale the same way each time, studies put the correlation with objective markers like %VO₂max and blood lactate above r > 0.80. That's a strong agreement for something this simple.