Heart Rate Zone Calculator

With the simple method, Zone 2 is 60% to 70% of your maximum heart rate. With the heart-rate reserve (Karvonen) method, it is resting HR plus 60% to 70% of the difference between max and resting HR. The reserve method is more individual because it accounts for your fitness.

A formula gives an estimate: 208 minus 0.7 times your age. It can be off by 10 beats or more either way. The most reliable number comes from a hard effort — the highest reading you see at the end of an all-out 5K or a set of hill repeats.

Easy. You can speak in full sentences and breathe through your nose if you try. It should feel almost too slow — that's normal, and it's the point.

For most runners, roughly 80% of weekly running time should be easy — Zones 1 and 2 — with the remaining 20% at moderate to hard intensity.

Heat, dehydration, poor sleep, stress, caffeine, hills and wrist-sensor error all push it up. It also drifts upward during long runs. If it's consistently high, slow down or add walk breaks; fitness will bring it down over weeks.

Yes. Rutz reads heart rate from your watch through Intervals.icu and uses it alongside pace to judge how hard each run really was, how your efficiency is trending and how much load you're carrying.