Heart-rate zones
calculator
Zone 2 base miles, zone 4 threshold, zone 5 sprints, but what are those in actual beats per minute for you? From age alone, or sharper with your resting heart rate.
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Two ways to set zones
The quick way estimates maximum heart rate as 220 minus age and takes zone percentages of that. The sharper way, the Karvonen method, uses your heart-rate reserve (max minus resting), which accounts for fitness: a lower resting HR shifts every zone to reflect your actual working range.
What each zone trains
Zone 2 is the famous one: easy, conversational effort that builds aerobic base and fat metabolism, where endurance athletes log most of their volume. Zones 3–4 raise sustainable race pace; zone 5 develops top-end power in short intervals. A common structure is ~80% of training time easy (zones 1–2), ~20% hard.
The honest caveat
"220 minus age" is a population average with real spread, true maxes commonly sit ±10–15 bpm from it. If you train seriously, a field-tested max or lab test beats the formula, and measuring your resting HR (on waking, still in bed) is the easiest accuracy upgrade. Anyone with a heart condition should set zones with a doctor. Pair with the pace calculator for the speed side.
Heart-rate zones FAQ
Estimate max HR as 220 minus age, then take percentage bands: zone 2 is 60–70%, zone 4 is 80–90%, and so on. Adding your resting HR switches to the more personalized Karvonen (reserve) method.
Easy, conversational-effort work at roughly 60–70% of max, the intensity where aerobic base and fat metabolism develop best. Most endurance programs put the bulk of weekly volume here.
It's a population average, individual true maxes commonly differ by ±10–15 bpm. Use it as a starting point; a field test or lab measurement, and the Karvonen option with real resting HR, tighten things up.
Because it measures your working range (reserve) rather than assuming it. Two people with the same age but different fitness get meaningfully different, and more accurate, zones.