The Borg RPE 6–20 scale vs the 1–10 RPE scale

The RPE 6 20 scale looks like it was designed by a committee that lost a bet. A rating scale that starts at 6? Ends at 20? Who rates their workout a 6?

There's a reason, and it's a good one. Gunnar Borg built the 6–20 scale so the numbers would roughly track heart rate: multiply the rating by 10 and you get something in the neighborhood of beats per minute. His later CR10 scale runs from 0 to 10 and behaves differently. And the 1–10 scale coaches use is a simplified cousin of that one. This post explains what each number on the 6–20 scale means, how it compares with the 1–10 versions, how to convert between them, and which one you should actually use. Short version: read research in 6–20, train in 1–10, which is the language used by an AI coach that plans your running and lifting together.

What is the RPE 6 20 scale?

The Borg Rating of Perceived Exertion scale runs from 6 to 20, where 6 is "no exertion at all" and 20 is "maximal exertion". It was initially designed to correspond to heart rate when multiplied by 10 (Carluccio et al., 2026). Borg developed it in the 1960s to put a number on how hard physical work feels (Tobase et al., 2024).

Between the endpoints sit verbal anchors. One study using the scale grouped them like this (Seo, Kim and Jung, 2022):

You rate the whole-body effort: breathing, heart, legs, how much you'd like to stop. It's still common in research, cardiology and rehab, and it shows up whenever a study says "RPE 13" or "RPE 15". It shows up less in training plans, which is why most programs, including our hybrid program, use a 1–10 scale instead.

If you want the general case for rating effort at all, start with rpe scale explained. This post is about the two Borg scales and how they fit together.

Why the scale starts at 6

Because of the heart rate design. Multiply the ends of the scale by 10 and you get 60 and 200 beats per minute, which spans roughly a resting heart rate to a young adult's estimated max (220 − 20 = 200). Rating × 10 ≈ heart rate was the idea.

That makes the scale useful in a lab, where heart rate and perceived effort are measured together. In a very large dataset of 2,560 people doing incremental treadmill or cycle tests, Borg RPE correlated strongly with heart rate (r = 0.74) and even more strongly with blood lactate (r = 0.83), and the relationship held regardless of sex, age, exercise type or activity level (Scherr et al., 2013).

Don't use the × 10 rule as a calculator, though. It assumes a max around 200, which by the common age formulas only fits people in their early twenties. A 50-year-old with a max of 173 who rates a run "17" is not at 170 beats per minute. It's a design idea, not a conversion.

What the 6–20 numbers mean for training

The research gives the 6–20 scale some useful anchors.

• ›Around 10–11: the first ventilatory threshold, the top of truly easy running (Bok, Rakovac and Foster, 2022).
• ›Around 13–15: the second threshold, the respiratory compensation point, roughly where hard-but-sustainable becomes unsustainable (same review).
• ›10.8 and 13.6: the average ratings at the lactate threshold and the individual anaerobic threshold in the Scherr dataset above.

Scherr and colleagues suggested 11–13 for less trained people and 13–15 when more intense but still aerobic training is the goal. On our scale, that's the jump from easy running to steady and tempo work.

The CR10 scale: Borg's 0–10 version

Borg's second scale is the category-ratio scale, CR10. It runs from 0 (no exertion) to 10 (maximal exertion) (Carluccio et al., 2026), with half-steps like 0.5 at the bottom, and it's used to rate exertion, pain and breathlessness (Tobase et al., 2024).

The difference isn't just the numbers. Borg designed it to combine a category scale with ratio properties (Borg, 1982), so the gaps between numbers aren't even. In a study of the CR scale during a maximal cycling test, ratings rose in a positively accelerating curve, like blood and muscle lactate, while heart rate rose in a straight line (Noble et al., 1983).

In plain English: on 6–20, each step is roughly the same size. On CR10, the jump from 7 to 9 is a lot bigger than the jump from 1 to 3. That matches how hard efforts actually feel. Going from easy to moderate is nothing. Going from hard to very hard is everything.

Borg 6–20 vs the 1–10 RPE scale

There are really three scales in circulation:

The coaching 1–10 scale used across this blog is a simplified version of the CR10 idea: 1 is lying on the sofa, 10 is the hardest thing you could possibly do. It's easier to remember at mile 9 than "was that a 14 or a 15?". For running, RPE in running covers how to pace every kind of run with it.

In the gym, 1–10 RPE usually means something more specific again. Lifters rate sets by how many reps were left: RPE 10 = 0 reps in reserve, RPE 9 = 1 rep in reserve, and so on, a scale formalized by Zourdos and colleagues (2016). That one has no 6–20 equivalent. Our guide to RPE for lifting explains what 7, 8 and 9 feel like under the bar, and our guide to reps in reserve covers how close to failure to train.

Converting the RPE 6 20 scale to 1–10

There's no official conversion, because the scales aren't built the same way. But for training, a practical mapping anchored to the thresholds above works well enough:

The logic: 10–11 marks the first threshold, which is the top of zone 2 on our model. 13–15 marks the second threshold, which zone 4 straddles. Everything else fills in around those two points. The zone column is the same five-zone model used everywhere on this blog; here's what each heart rate zone does if you want the detail.

Treat it as a translation guide for reading studies, not a precise conversion. If a paper prescribes "RPE 13–15", read it as steady to tempo effort, roughly 6–8 on your scale.

Which scale should you use?

• ›Training: 1–10. It's quicker, it's what most plans use, and it works for runs and lifts.
• ›Reading research: know the 6–20 anchors. Most exercise studies that report RPE use it.
• ›Rehab or medical settings: use whatever your clinician uses. If you're exercising after a heart condition or under medical supervision, follow their scale and their limits, not this table.

Whichever scale you use, the rules are the same: rate the hard part of the effort, not how you felt walking in; be honest on both easy and hard days; and if the rating and the plan disagree, believe the rating.

Common Borg scale mistakes

• ›Using rating × 10 as your heart rate. It's a design intention for an average young adult, not a formula.
• ›Mixing scales in one plan. "RPE 8" means hard on 1–10 and very light on 6–20. Know which one you're reading.
• ›Treating the scales as interchangeable point for point. CR10 is accelerating; 6–20 is roughly linear. Convert by effort, not by arithmetic.
• ›Rating easy runs too high. On 6–20, a true easy run sits around 9–11. If your "easy" runs are 13, they're steady runs.

How exrsz uses RPE

exrsz builds a periodized plan from your goal, schedule, level and equipment, and gives every run and lift an intensity target in one 1–10 language. It balances hard and easy sessions across running and lifting in one plan, adapts each week to how you actually trained, and reshuffles missed sessions.

FAQ

What is the RPE 6 20 scale?

It's Gunnar Borg's Rating of Perceived Exertion scale, running from 6 (no exertion at all) to 20 (maximal exertion). It was designed so the rating multiplied by 10 roughly corresponds to heart rate (Carluccio et al., 2026).

Why does the Borg scale go from 6 to 20?

Because it was designed to line up with heart rate: 6 × 10 is 60 and 20 × 10 is 200 beats per minute. Rating × 10 is a rough guide, not a precise conversion.

How do I convert Borg 6–20 to a 1–10 RPE?

There's no official conversion, but a practical one is 9–11 ≈ RPE 3–4 (easy), 12–13 ≈ 5–6 (steady), 14–16 ≈ 7–8 (tempo) and 17–20 ≈ 9–10 (very hard to maximal).

What is the difference between the Borg RPE scale and CR10?

The 6–20 scale rises roughly in line with heart rate, while CR10 runs 0–10 and rises in an accelerating curve, more like blood lactate (Noble et al., 1983).

What Borg rating is a good training intensity?

One large study suggested 11–13 for less trained people and 13–15 for more intense but still aerobic training (Scherr et al., 2013).