Heart rate zones: how to calculate them properly (and why 220 − age is not enough)
Heart rate zones are the most widely used tool for controlling training intensity — and the worst configured. If you have never measured your true maximum heart rate, your zones almost certainly do not match your physiology.
Why 220 − age is not enough
The classic 220 − age formula has a standard error of ±10 to ±12 beats per minute, and it usually underestimates trained athletes. Get your maximum heart rate wrong and every percentage shifts: what you think is zone 2 may in fact be zone 3, which is the mistake that limits progress the most.
Before calculating zones, check that your watch or chest strap is giving you reliable data. In Afterpacer you can inspect the full heart rate curve of every activity to spot dropouts, impossible spikes or values stuck on a fixed number — clear signs of a failing sensor.
How to measure your real maximum heart rate
You need a progressive effort all the way to the limit. Two protocols that work well for runners:
- 30-minute test: after 15 minutes of easy warm-up, run 30 minutes flat out and take the average of the last 20. Estimate your maximum as
average + 5 %. - Long hills: 3-minute repeats on a gradient with incomplete recovery, pushing hard in the final 30 seconds of each. Maximum heart rate shows up in the last or second-to-last repetition.
If you have a cardiac history or any doubt, get a medical exercise test: it is the most reliable method and the only one that can detect problems.
Defining the five zones
With maximum heart rate as the reference, the usual percentage zones are:
| Zone | % of max HR | Feels like | What it is for |
|---|---|---|---|
| Z1 Recovery | 50–60 % | Very easy, nasal breathing | Active recovery, warm-up |
| Z2 Aerobic base | 60–70 % | Conversational | Volume, efficiency, fat oxidation |
| Z3 Tempo | 70–80 % | Short sentences | Sustained pace, marathon |
| Z4 Threshold | 80–90 % | Hard, heavy breathing | Lactate threshold, 10K to half marathon |
| Z5 Maximum | 90–100 % | Cannot speak | Intervals, VO2max, surges |
In Afterpacer you can store your maximum heart rate (or fully custom zones) in your profile and every activity is reclassified automatically: you will see how much time you spend in each zone, per activity and accumulated for the week.
How to train with them without obsessing
- Respect Z2. It is the most abused zone: if a hill pushes your heart rate into Z3, walk or slow down. The goal is time, not pace.
- Alternate hard and easy. Roughly 80 % in Z1–Z2 and 20 % in Z3–Z5 works for most amateur runners.
- Watch heat and elevation: the same effort at 30 °C or uphill produces a higher heart rate. Zones measure effort, not performance.
- Review every 6–8 weeks. Your maximum heart rate changes with fitness and age; revisit your zones too.
Combining heart rate and pace
Heart rate is reactive: it takes time to rise and to fall. Pace, power and elevation complement it. The most informative signal is the relationship between the two: holding the same pace at a lower heart rate under the same conditions is the clearest proof that you have improved.
To see all of this in practice, open the demo with a real activity: map, splits, elevation and heart rate, no account needed.