Polar Flow shows your heart rate zones after a workout, but the questions usually come before it: what is my max heart rate, where does easy end, and which zone is 148 bpm? We built Beat Zones to answer those in a few seconds. It is a free heart rate zone calculator and pulse counter that runs right here in your browser. No install, no signup, and it opens with a real example already filled in.
Find your zones now
Set your age and resting heart rate, pick a method, and watch the zone bar and table move. Type a live reading, or count your own pulse for 15 seconds.
How to use Beat Zones
Drag the age and resting heart rate sliders, or use the plus and minus buttons for single steps. Choose Tanaka, Karvonen or % HRmax. The zone bar and the table below it update on every change, with no Calculate button. The marker slides to your live reading, and the headline tells you which zone it falls in.
To count your pulse, find it at your wrist or neck and tap the big pad on each beat. The 15 seconds start on your first tap and we multiply the count by 4. The result becomes your live reading, and you can send it to the resting rate field too.
Logging a reading or finishing a count keeps a daily streak going. Your inputs and streak live on your device. Nothing leaves your browser.
These are estimates for general fitness information, not medical advice. The formulas describe population averages, so your own limits can differ.
How it compares to Polar Flow
Beat Zones keeps the part of a heart rate app you use before and after exercise: working out max heart rate, turning it into five zones, and checking where a number sits. It drops the rest. There is no sensor connection, no workout recording, no history, no training load and no account.
Polar Flow records sessions from compatible Polar devices and shows time in each zone afterwards. Some of its features depend on that hardware, and we did not try to fake any of it in a tab. The three methods here also differ: Tanaka uses 208 minus 0.7 times age, % HRmax uses the older 220 minus age, and Karvonen adds your resting rate through heart rate reserve.
Our advice is to use Beat Zones to set ranges and sanity-check a reading. Use the app and a chest strap or watch for real tracking. If your numbers keep landing outside the estimate, a lab test or a clinician gives a better answer than any formula. For pace and interval planning, try our running pace calculator and HIIT interval timer. Our roundup of continuous heart-rate tracking apps covers the wearables side.
Get the full app
Polar Flow is available on Android and works with Polar sports watches and sensors. It syncs your sessions and breaks them down by zone.
Frequently asked questions
How do I calculate my heart rate zones?
Start with an estimated max heart rate, then take percentages of it. The five zones here run 50 to 60, 60 to 70, 70 to 80, 80 to 90 and 90 to 100 percent. With the Karvonen method the percentages apply to the gap between your resting and max rate instead, then add the resting rate back.
What is the difference between Tanaka and 220 minus age?
The older 220 minus age formula is simple but tends to be off for many adults. Tanaka, 208 minus 0.7 times age, came from a larger analysis and is usually a little lower for young people and higher for older ones. Both are averages, so treat either as a starting point.
Which zone is best for fat loss or fitness?
There is no single best zone. Zone 2 is the easy aerobic range many people use for most of their training, and the harder zones are used sparingly. What suits you depends on your goal, health and experience.
How do I measure my resting heart rate?
Sit quietly for a few minutes or measure just after waking. Count beats for 15 seconds with the pulse counter above and use the Use as resting rate button. Repeat on a few mornings for a steadier figure.
Is this the real Polar Flow?
No. Beat Zones is an original tool we built, inspired by the zone side of heart rate training. It is not affiliated with, endorsed by, or connected to Polar. It does not read any sensor and is not medical advice. For recording workouts, get the official app from the stores above.
Is it free, and does it work offline?
Yes. It is free, needs no signup, and works offline once the page has loaded. Your last inputs and your streak are saved in your browser’s local storage on your device only.
