FluxRun AIFree running calculators › Heart rate zones
Heart rate zone calculator
Work out your five running heart rate zones from your age, or better, from your measured maximum heart rate.
| Zone | Heart rate | Feels like |
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Not medical advice. If you have a heart condition, ask your doctor before training by heart rate.
How your zones are calculated
Each zone is a range of your maximum heart rate. If you enter only your age, the calculator estimates your maximum with the Tanaka formula: 208 − 0.7 × age. That's an estimate: real maximum heart rates vary a lot between people of the same age, so if you know your measured maximum (for example from a hard uphill effort with a chest strap), enter it and it will be used instead.
If you also enter your resting heart rate, the calculator switches to the heart rate reserve method: each zone becomes your resting heart rate plus a percentage of the difference between your maximum and resting heart rate. This takes your own fitness into account and usually gives slightly higher numbers for the easy zones.
What the five zones are for
Zone 1 (50–60 %) is very easy: warm-ups, cool-downs and recovery runs. Zone 2 (60–70 %) is easy running, and it's where most of your running should be: you can talk in full sentences. Zone 3 (70–80 %) is steady, comfortably hard. Zone 4 (80–90 %) is around your threshold, the effort you could hold for roughly an hour in a race. Zone 5 (90–100 %) is for short, hard intervals.
Many new runners spend almost all their time in zone 3 because easy running feels too slow. Slowing down to zone 2 for most runs usually makes the hard sessions better and the whole week more sustainable.
Wrist readings and heart rate lag
Optical sensors on watches can read high or low, especially in the cold or during fast changes of pace. A chest strap is more accurate. Heart rate also takes a minute or two to catch up when you speed up, so judge short intervals by effort and pace, and use heart rate mainly for steady runs.
Heat, tiredness and caffeine
Your heart rate for the same pace changes from day to day. Hot weather, poor sleep, illness, stress and caffeine can all push it up by several beats. If your easy pace suddenly puts you in a higher zone, it's usually a sign to slow down rather than a sign you've lost fitness. Look at the trend over a few weeks, not a single run.
FAQ
What is zone 2 running?
Easy running at 60–70 % of your maximum heart rate, slow enough to talk. It's where most of a runner's weekly distance usually goes.
Is 220 minus age accurate?
It's a rough estimate. This calculator uses the Tanaka formula (208 − 0.7 × age), which is also an estimate. A measured maximum heart rate is better.
Should I use heart rate reserve?
If you know your resting heart rate, yes: entering it switches the calculation to heart rate reserve, which accounts for your own fitness.
How do I find my resting heart rate?
Measure it in the morning, lying still, before you get up. Many watches also show it.
Want a plan that does this for you?
Flux Run builds your weekly running plan, talks you through every run and adapts after each one. Free on iPhone and Android.
