Heart rate zone calculator
Free heart rate zone calculator for runners. Find your 5 training zones and your Zone 2 heart rate from age, max HR and resting HR (Karvonen method).
| Zone | bpm | What it's for |
|---|---|---|
| 1 | 92–110 | Recovery — very easy, warm-ups |
| 2 | 110–128 | Aerobic base ("Zone 2") — easy, conversational |
| 3 | 128–147 | Tempo — comfortably hard |
| 4 | 147–165 | Threshold — hard, sustainable ~1 hour |
| 5 | 165–184 | VO2max — very hard, short intervals |
In Bangkok's heat your heart rate drifts upward during a run, so staying in Zone 2 may mean running much slower than you expect. That's normal — it's still doing its job.
How it works
Max heart rate is estimated with the Tanaka formula, 208 − 0.7 × age, unless you enter your own (a field test or race is more accurate).
If you add your resting heart rate, zones use the Karvonen method — percentages of your heart-rate reserve (max − resting) — which fits individuals better than plain % of max.
Zone 2 is the easy aerobic zone where most of your weekly running should happen. It builds the endurance everything else sits on.
FAQ
What is Zone 2 running?
Easy running at roughly 60–70% of your heart-rate reserve — slow enough to talk in full sentences. It builds aerobic fitness with little fatigue.
Why is my Zone 2 pace so slow in Bangkok?
Heat and humidity push your heart rate up for the same pace (cardiac drift). Running by heart rate means slowing down on hot days — that's expected and still effective.
How do I find my real max heart rate?
A hard race finish or a supervised test gives a better number than any formula. Formulas can be 10+ bpm off for individuals.
Results are estimates for planning training, not medical advice.