Borg RPE Scale: Calculator, Zones and Heart Rate

The Borg rating of perceived exertion asks one question no device can answer for you: how hard does this feel right now? Slide to the number that matches the effort and the calculator returns the training zone it falls in, plus the heart rate the classic RPE times 10 rule would predict.

What the numbers stand for

Gunnar Borg anchored the 6 to 20 range with short verbal descriptions rather than percentages. The low end, 6 through 8, is no exertion to extremely light; 9 and 10 are very light; 11 and 12 are light; 13 and 14 are somewhat hard, the anchor most guidelines lean on for moderate work; 15 and 16 are hard; 17 and 18 are very hard; 19 is extremely hard; and 20 is maximal exertion. Odd numbers sit between two anchors on purpose, so you can grade an effort finely without inventing words for it.

The scale and its wording belong to Gunnar Borg and are administered under license by Borg Perception: the Rehabilitation Measures Database records a fee of up to $1,100 for large organizations requesting use of the scale. The anchors are described here as reference, not as a substitute for the licensed form. The full number-by-number reference goes through each rating and what people usually mean by it; this page is the calculator that turns a rating into a zone.

How the calculator groups the ratings

Rating	Zone shown
6 to 10	Light
11 to 14	Moderate
15 to 18	Vigorous
19 to 20	Maximal

Treat those cuts as a working simplification, not a published boundary. Borg’s own descriptor for 11 and 12 is light, and this grouping still files them under the moderate zone — a reminder that the zone label is a convenience layered on top of the scale, while the descriptor is the scale itself.

The federal Physical Activity Guidelines for Americans use a different and simpler ruler for the same idea: a 0 to 10 scale of relative effort where “sitting is 0 and the highest level of effort possible is 10”, moderate activity is a 5 or 6, and vigorous begins at 7 or 8. If you have seen both and wondered which is right, they are two scales of the same construct, and the 0 to 10 one is what U.S. public health documents quote.

How well the rating tracks what a lab would measure

The largest test of this is a cohort of 2,560 adults, median age 28, who did incremental treadmill or cycle tests while heart rate, blood lactate and RPE were recorded at the end of every stage. RPE correlated strongly with heart rate (r = 0.74) and with blood lactate (r = 0.83). More useful for training: the lactate threshold fell at an average RPE of 10.8 and the individual anaerobic threshold at 13.6.

The same paper reported that sex, age, coronary artery disease, activity level and whether the test ran on a treadmill or a bike “did not influence this association significantly”, and its practical recommendation was an RPE of 11 to 13 for less trained people and 13 to 15 for harder but still aerobic work.

Worked example

You settle into a run that feels manageable and rate it 13. The calculator files that in the moderate zone, with the descriptor somewhat hard, and prints an estimated 130 bpm. Push the pace until it reads 17 and the zone becomes vigorous, with an estimate of 170 bpm. The zone change is the meaningful part; the bpm figure carries an error band that grows with your age, which is the subject of the RPE to heart rate page.

When to reach for effort instead of a number on a watch

Perceived effort holds up where heart rate misleads: lifting, circuits with stops, swimming, hot weather, and anyone on medication that changes heart rate. The full comparison of the two methods sets out which one to trust in each situation, and the heart rate zone calculator builds the bpm-based version from your age if you would rather work in beats per minute.

Two groups get their own version of this advice: pregnancy, where the American College of Obstetricians and Gynecologists prefers effort over heart rate and pairs it with the talk test, and older adults, where relative intensity beats absolute intensity — see the RPE scale for seniors.

This content is informational and does not replace medical evaluation, particularly if you have a heart condition or are starting exercise after a long break.