Endurometry
Build zones from your own max and resting heart rate with Karvonen reserve, not 220 minus age alone. Most weekly volume belongs in Z2. Wrist sensors lag on intervals; a chest strap is the reference.
Last updated October 5, 2026
Heart rate zones are not magic, but they are the cheapest feedback loop in running: one number that tells you whether today is easy or hard, regardless of how you feel at kilometre two. The trick is calculating them from your own numbers and then respecting them.
Work out your own numbers first
Two inputs decide everything: maximum heart rate and resting heart rate. The age formula (220 − age) is a population average with a standard deviation of about 10–12 bpm — it is a starting point, not a measurement. Your resting HR is easy to measure properly: take it lying in bed before you get up, three mornings in a row, and use the average.
Then use the heart rate zone calculator, which applies the Karvonen method (heart-rate reserve) rather than plain percentages of max. The distinction matters: two runners both aged 35 can have zones that differ by 10 bpm.
What the zones are for
| Zone | Feels like | What it trains |
|---|---|---|
| Z1 – recovery | Conversation with no effort | Blood flow, the day after a hard session |
| Z2 – easy / aerobic base | Full sentences, nose breathing possible | The bulk of your weekly volume; fat oxidation and capillary density |
| Z3 – steady / marathon | Short sentences | Marathon-specific pace and fuelling practice |
| Z4 – threshold | A word or two, comfortably hard | The pace you can hold for about an hour |
| Z5 – intervals | Cannot speak | VO2max, sharpening, short repeats only |
Most amateur runners spend too much time in Z3 and not enough in Z2 or Z4 — the middle zone is hard enough to tire you and easy enough to give nothing back.
The sensor question
Wrist-based optical heart rate is fine for steady running and genuinely convenient. It is much less reliable for intervals, cold weather, and anything under a long sleeve, because the sensor is measuring blood flow through a wrist that is moving. A chest strap measures the electrical signal from your heart directly and is the reference every wrist sensor is compared against. If your intervals show a heart rate that jumps around or lags 30 seconds behind your legs, that is the sensor, not you.
If you would rather run by pace than by heart rate, the training pace calculator gives you the equivalent zones derived from a recent race result — many runners find pace easier to hold steadily than HR.
Related Tools
Heart Rate Zone Calculator
Calculate your five running heart-rate zones from age, resting heart rate and max heart rate using the Karvonen method.
Training Pace Calculator (VDOT Zones)
Get your VDOT from a recent race and see easy, marathon, threshold, interval and repetition pace zones plus heart-rate zones.
Race Time Predictor
Predict your finish time at any distance using the Riegel power law and the Daniels–Gilbert VO2max model.
Related guides
Pace vs heart rate training
Pace and heart rate describe the same session in two languages. When to follow which, why Karvonen Z2 looks “high” on a %HRmax watch, and what cardiac drift is doing on a long run.
Easy, Tempo and Long Run Paces
One comparison table for the three intensities every plan is built from: easy, tempo and the long run — with heart-rate %, VDOT % and the pace range that goes with each.
How the numbers are calculated
Frequently Asked Questions
Is 220 minus age accurate?
It is a population average with roughly ±10–12 bpm of spread. Useful as a starting estimate, worth replacing with anything you have measured.
Why is my heart rate high on easy runs?
Heat, caffeine, dehydration, fatigue and altitude all raise HR at the same pace. If it is a one-off, ignore it; if it is every day, slow down.
Do I need a chest strap?
For steady runs, no. For intervals and cold-weather sessions, it is the difference between data you can act on and data you have to guess about.
Want a new tool or fix?
Tell us which calculator, pace chart or fix would help — we build what runners ask for. Replies usually come back in 1–2 days.