Beatcast
Karvonen formula calculator
Updated
What this does
Enter your age or a measured maximum, and your resting heart rate. The calculator applies the Karvonen formula and shows five zones in beats per minute. Everything runs in your browser. Nothing you type is sent, stored or logged.
The calculator
Whole years, 10 to 100.
How the zones are worked out.
Five is Beatcast's default.
Optional, 100 to 230 bpm. Left empty, the Tanaka estimate from your age is used.
Optional, 30 to 120 bpm. The Karvonen method needs it.
Optional, 80 to 220 bpm. Percent of threshold needs it.
The formula
Karvonen works on your heart rate reserve, which is the gap between your maximum and your resting rate.
Reserve = maximum minus resting.
Target = resting plus reserve times the share.
Beatcast's five zones start at 50, 60, 70, 80 and 90 percent. A zone runs from its lower number up to, but not including, the next one. The top zone has no ceiling. Karvonen and colleagues described the method in 1957.
A worked example
Age 40, resting heart rate 60. Tanaka gives a maximum of 208 minus 28, which is 180. The reserve is 180 minus 60, which is 120.
| Zone | Name | Range (bpm) | Share of reserve |
|---|---|---|---|
| 1 | Recovery | 120 to 131 | 50 to 60% |
| 2 | Endurance | 132 to 143 | 60 to 70% |
| 3 | Tempo | 144 to 155 | 70 to 80% |
| 4 | Threshold | 156 to 167 | 80 to 90% |
| 5 | Max | 168 and up | 90% and up |
Zone 2 starts at 60 plus 0.6 times 120, which is 132. The percent of maximum method gives 108 for the same person. That is why two zone 2 numbers can sit 24 beats apart. The zone 2 calculator lays the definitions side by side.
When Karvonen fits
It suits you if you know your resting rate and trust it. It moves the zones with fitness, since a lower resting rate widens the reserve. It is only as good as the resting number you give it, and a resting rate varies with sleep, caffeine and the day.
Limits
Karvonen needs a maximum. If you have no measured one, the estimate from age can be roughly a dozen beats off for one person (Nes and colleagues reported a standard error of 10.8 in 2013), and that error carries into every zone. See the max heart rate calculator.
These are training estimates. If you take medication that changes your heart rate or have a heart condition, ask your clinician before using age-based numbers. Beatcast is not a medical device.
Beatcast uses these numbers
Choose Karvonen as the model in a zone profile and enter your resting rate in Personal details. The zone profile names the formula it uses. Beatcast on the App Store. Fourteen days free, then one purchase.
For the other methods, see heart rate zones explained.
Questions
What is heart rate reserve?
Maximum minus resting heart rate.
Is Karvonen better than percent of maximum?
Neither is right for everyone. Karvonen uses one more number about you.
What is my reserve at 40 with a resting rate of 60?
120, using Tanaka for the maximum.
Can I enter my own maximum?
Yes. A measured one is used in place of the estimate.
Good to know
Beatcast is not a medical device. It is built for training and general wellbeing, and it cannot detect, diagnose, treat or monitor any condition. If something about your heart worries you, talk to a doctor rather than to an app.
Apple and iPhone are trademarks of Apple Inc. All other names belong to their owners. Beatcast is an independent product and is not affiliated with, endorsed by or certified by any of them.