Heart Rate Training Zone Calculator
Example: Age: 35 years · Resting heart rate: 60 bpm
| Estimated max heart rate | 185 |
| Zone 2 low (aerobic base) | 135 |
| Zone 2 high | 147.5 |
| Zone 4 low (threshold) | 160 |
| Zone 4 high | 172.5 |
Worked example
For a 35-year-old with a resting heart rate of 60, estimated max is 220 - 35 = 185 bpm, so heart-rate reserve is 185 - 60 = 125 beats. Zone 2 (60 to 70% of reserve) runs from 60 + 0.60 x 125 = 135 up to 60 + 0.70 x 125 = 148 bpm. Zone 4 (80 to 90%) runs from 160 to 173 bpm. Easy aerobic runs live in the first band; threshold intervals live in the second.
Frequently asked questions
Why use the Karvonen method instead of percent of max heart rate?
Karvonen uses your heart-rate reserve, the gap between resting and max, so it accounts for your individual fitness. A fitter person with a lower resting heart rate gets zones shifted to reflect that, which the plain percent-of-max method ignores. The result is a more personal and usually more accurate set of zones.
How do I find my true maximum heart rate?
The 220-minus-age formula this tool uses is a population estimate that can be off by 10 to 20 beats for any individual. A supervised maximal test or a hard, well-monitored effort gives a truer number. If you know your tested max, your real zones may differ from these estimates.
How do I measure resting heart rate correctly?
Measure it first thing in the morning before you get out of bed, ideally averaged over several days. Caffeine, stress, and poor sleep raise it. A wearable that tracks overnight resting heart rate gives a reliable figure to enter here.
How much time should I spend in each zone?
Most endurance plans put the large majority of training in the easy zone-2 range to build an aerobic base, with a smaller dose of harder zone-4 threshold work. This polarized balance is a common reason experienced athletes keep improving without burning out.