Heart Rate Reserve Formula
Learn the Heart Rate Reserve (HRR) formula and the Karvonen method for calculating personalized training heart rate zones.
The Formula
HRR = HRmax − HRrest
Heart Rate Reserve is the gap between your maximum and resting heart rate — your usable cardiovascular range during exercise.
Karvonen Target Heart Rate
Target HR = HRrest + (Intensity% × HRR)
Use this to find the exact heart rate that corresponds to any training intensity percentage.
Maximum Heart Rate Estimate
HRmax ≈ 220 − Age
This is a widely used estimate. For greater accuracy, measure your max HR during an all-out effort test under supervision.
Variables
| Symbol | Meaning | Unit |
|---|---|---|
| HRR | Heart Rate Reserve | bpm |
| HRmax | Maximum heart rate | bpm |
| HRrest | Resting heart rate | bpm |
| Intensity% | Desired training intensity as a decimal | 0–1 |
| Target HR | Heart rate to aim for during training | bpm |
Example 1 — Calculate HRR
A 35-year-old athlete with a resting HR of 55 bpm.
HRmax ≈ 220 − 35 = 185 bpm
HRR = 185 − 55 = 130 bpm
Heart Rate Reserve = 130 bpm
Example 2 — Zone 2 Target HR
Using the same athlete, find Zone 2 (65% intensity) target HR.
Target HR = 55 + (0.65 × 130)
Target HR = 55 + 84.5
Target HR ≈ 140 bpm for Zone 2 aerobic training
Karvonen Training Zones
| Zone | HRR % | Purpose |
|---|---|---|
| Zone 1 | 50–60% | Recovery and warm-up |
| Zone 2 | 60–70% | Aerobic base building |
| Zone 3 | 70–80% | Aerobic threshold |
| Zone 4 | 80–90% | Lactate threshold |
| Zone 5 | 90–100% | VO2 Max / max effort |
When to Use It
- Setting personalized training zones for any sport
- Ensuring recovery runs stay truly easy
- Structuring interval and threshold workouts precisely
- Monitoring cardiovascular fitness over time