Heart Rate Zone Calculator
Five zones, two methods: the simple percentage-of-max approach and the Karvonen method, which accounts for your resting heart rate and usually fits trained runners better.
Your numbers
Measure it in bed, before getting up, on three mornings and average them.
Result
Your result appears above and updates as you type.
How it works
Everything starts from maximum heart rate, estimated here as 220 minus age. That formula has a standard deviation of roughly ±10–12 bpm, so the zones it produces are neighbourhoods, not addresses. The Karvonen method improves things by working with heart-rate reserve — the gap between your resting and maximum rates — so a fit runner with a resting rate of 48 gets different, more realistic zones than a beginner with the same age and a resting rate of 74.
Zone 2 is where most endurance is built: conversational pace, roughly 60–70%. Zone 4 is threshold — comfortably hard, sustainable for about an hour when fit. Zone 5 is for short intervals only, and no training plan needs much of it.
Good practice & limits
- If you know your true max from a hard race or lab test, trust it over any formula and adjust the age input until the estimate matches.
- Chest straps read far more reliably than wrist sensors during intervals and in cold weather.
- Zones drift with heat, caffeine, illness and fatigue. A Zone 2 heart rate at a slower pace on a hot day is the system working, not failing.