Karvonen Heart Rate Calculator
Calculate target heart rate training zones using the Karvonen formula.
Enter age and resting heart rate to find your personalized intensity zones for exercise.
The Karvonen formula calculates target heart rate by accounting for your resting heart rate — making it more personalized than the simple age-based percentage method.
The key concept is Heart Rate Reserve (HRR): the range between your resting heart rate and your maximum heart rate. You are training within a percentage of that reserve, not your maximum.
HRmax = 220 - Age HRR = HRmax - Resting Heart Rate Target HR = (HRR x Intensity%) + Resting Heart Rate
For a 35-year-old with a resting HR of 60 bpm training at 70% intensity: HRmax = 185 bpm HRR = 185 - 60 = 125 bpm Target HR = (125 x 0.70) + 60 = 147.5 bpm
Compare this to the simple method: 185 x 0.70 = 129.5 bpm. That is an 18-bpm difference — significant enough to push someone into a completely different training zone.
The five standard zones:
- Zone 1 (50-60%): Recovery and light activity. Comfortable conversation pace.
- Zone 2 (60-70%): Fat burning. The aerobic base most endurance athletes build on.
- Zone 3 (70-80%): Aerobic. Breathing is harder; full sentences become short sentences.
- Zone 4 (80-90%): Threshold. Sustainable for only 20-40 minutes for most people.
- Zone 5 (90-100%): Maximum effort. Intervals, sprints, and race finishes.
Note: the 220 - age formula for HRmax is an average estimate with high individual variability. If you have had a recent maximum heart rate test, you can substitute that value for a more accurate result. Consult a healthcare provider before beginning a new exercise program.