What is Rate of Perceived Exertion (RPE)?
Rate of perceived exertion (RPE) is a scale from 1 to 10 (or 6 to 20 in the original Borg scale) that measures how hard you feel like you're working during exercise — a practical, self-reported tool for matching training intensity to your readiness on any given day.
Rate of perceived exertion (RPE) is a scale used to quantify the subjective intensity of physical exercise — how hard you feel like you're working, independent of external measurements like heart rate or weight on the bar. It was first developed by Swedish psychologist Gunnar Borg, and has since become a foundational tool in both cardio programming and strength training.
RPE allows athletes and coaches to communicate intensity in a way that accounts for individual variation and daily fluctuations in energy, recovery, and stress — something fixed prescriptions like "lift 80% of your 1RM" can't do.
The Borg Scale (Original)
The original Borg RPE Scale runs from 6 to 20, with each number roughly corresponding to heart rate when multiplied by 10 (so RPE 15 ≈ heart rate ~150 BPM):
| Borg Scale | Description |
|---|---|
| 6 | No exertion at all |
| 9 | Very light (easy walk) |
| 11 | Light |
| 13 | Somewhat hard |
| 15 | Hard |
| 17 | Very hard |
| 19 | Extremely hard |
| 20 | Maximum exertion |
This scale is still used in clinical and research settings, particularly in cardiopulmonary rehabilitation.
The Modified RPE Scale (1–10)
Most athletes and coaches now use a simplified 1 to 10 scale, which is more intuitive:
| RPE | Description | Cardio Example | Strength Example |
|---|---|---|---|
| 1–3 | Very easy, minimal effort | Slow walk | Warm-up sets |
| 4–5 | Light to moderate | Brisk walk | Very easy lift |
| 6–7 | Moderate to hard | Jog, cardio zone 3 | Working sets with several reps left |
| 8 | Hard, challenging | Tempo run | 2 reps left in the tank |
| 9 | Very hard, near max | Near-sprint intervals | 1 rep left |
| 10 | Maximum effort, can't continue | All-out sprint | True 1-rep max attempt |
RPE in Strength Training: Reps in Reserve (RIR)
In powerlifting and strength training, RPE is often expressed alongside reps in reserve (RIR) — how many more reps you could have completed before failure:
| RPE | RIR (Reps Left in Tank) |
|---|---|
| 10 | 0 — could not do another rep |
| 9 | 1 |
| 8 | 2 |
| 7 | 3 |
| 6 | 4 |
| 5 or below | 5+ reps left |
A program that prescribes "4 sets of 5 reps at RPE 8" means: use a weight that feels like you had about 2 reps left after each set. You then adjust the weight based on how each set feels — this is called autoregulation.
RPE vs. Heart Rate Monitoring
| RPE | Heart Rate | |
|---|---|---|
| Equipment needed | None | Heart rate monitor |
| Accounts for daily readiness | Yes | Partially |
| Accurate for high-intensity efforts | Yes | Less reliable at extremes |
| Best for | Strength training, perceived effort | Aerobic cardio zones |
| Learning curve | Moderate (takes calibration) | Low |
RPE is especially valuable when heart rate monitors are impractical (e.g., during barbell lifts) or when cardiac drift (heart rate rising over a long session despite constant pace) makes zone-based training harder to follow.
Limitations of RPE
- Subjective — Two people at "RPE 8" may actually be working at very different intensities
- Requires experience — Beginners often underestimate or overestimate their RPE; it takes time to calibrate your internal scale accurately
- Doesn't account for technical breakdown — You might have reps in the tank but your form breaks down before you reach true muscular failure
Despite these limitations, RPE is widely regarded as a practical, scalable tool for managing training intensity — especially for intermediate and advanced athletes who know their bodies well.
Using RPE With Heart Rate Zones
For cardio training, RPE roughly maps to common heart rate zones:
- Zone 2 (aerobic base building): ~RPE 4–5
- Zone 3 (moderate, "tempo"): ~RPE 6–7
- Zone 4 (threshold): ~RPE 8–8.5
- Zone 5 (VO2 max): ~RPE 9–10
This mapping makes RPE a convenient backup when heart rate data isn't available or reliable, such as during early morning training when resting heart rate varies, or during hot-weather exercise when cardiovascular drift inflates heart rate.