Quick Summary
RPE (Rate of Perceived Exertion) is a simple way to measure how hard exercise feels using a 6–20 scale.
For Zone 2 cardio, aim for an RPE of 12–13 out of 20 — a steady, moderate effort where breathing is deeper but controlled, and you can still speak in short sentences.
RPE stands for Rate of Perceived Exertion.
It’s a simple way to estimate how hard your body is working during exercise—based on how it feels, not on devices or formulas.
The 20-point Borg RPE scale was designed to roughly correlate with heart rate. For example:
- An RPE of 12 ≈ ~120 beats per minute
- An RPE of 14 ≈ ~140 beats per minute
This makes it especially useful if you don’t wear a heart-rate monitor or if your heart rate is affected by medications, fatigue, or stress.
The 20-Point RPE Scale (Simplified)
- 6–8: Very, very light
Easy movement, barely any effort - 9–11: Light
Comfortable, warm-up pace - 12–13: Moderate, steady effort (Zone 2)
Breathing is deeper but controlled
You can still talk in short sentences
Feels sustainable for a longer period - 14–16: Hard
Breathing is heavy, conversation is difficult - 17–20: Very hard to maximal
Short bursts only, not sustainable
What Is Zone 2 Cardio?
Zone 2 cardio is a moderate, steady level of exercise that you can maintain for an extended time without exhaustion.
On the 20-point RPE scale, Zone 2 typically falls between 12 and 13.
At this intensity:
- You feel like you’re working, but not pushing
- Your breathing is faster, yet controlled
- You could continue for 20–60 minutes
- You finish feeling energized, not depleted
How to Use RPE to Stay in Zone 2
- Start your activity (walking, cycling, elliptical, rowing, etc.).
- After a few minutes, check in with your body:
- How hard does this feel overall?
- Could you continue at this pace?
- Adjust your effort until it feels like a 12–13 out of 20.
- Re-check your RPE periodically, especially if:
- You increase speed or resistance
- You feel fatigue setting in
If your effort drifts above 13, slow down slightly.
If it feels easier than 12, gently increase the pace.
Why RPE Works
RPE is flexible and self-regulating. It accounts for:
- Daily energy levels
- Stress and sleep
- Medications that affect heart rate
That makes it a reliable, practical way to guide Zone 2 cardio—especially when consistency matters more than precision.