Heart Rate Zone Calculator
Five zones, each with a job. Computed with the Karvonen method, which uses your resting pulse to personalise the ranges instead of age alone.
Why your resting pulse is in the formula
Two people the same age can have resting pulses of 50 and 80 — the plain “220 minus age” zones would prescribe them identical targets, which is clearly wrong. The Karvonen method works from your heart rate reserve (max minus resting), so a fitter heart gets appropriately harder targets. Measure resting pulse in bed before getting up, three mornings, and average.
What each zone is for
- Zone 1 — Recovery. Genuinely easy movement that speeds recovery without adding fatigue.
- Zone 2 — Endurance. The base. Builds mitochondria, teaches the body to burn fat, and can be done in volume day after day. Most people train this zone too hard, which turns it into junk mileage.
- Zone 3 — Tempo. “Comfortably hard.” Useful, but easy to overuse — hard enough to fatigue, not hard enough to force top-end adaptation.
- Zone 4 — Threshold. Intervals of 4–10 minutes here raise the pace you can sustain. This is where hard cardio sessions belong.
- Zone 5 — Max. Short sprints for power and peak capacity. Seconds, not minutes.
The 80/20 rule is the most reliable finding in endurance training: about 80% of cardio time in Zones 1–2, 20% in Zones 4–5, and surprisingly little in the middle. Easy days easy, hard days hard.
About the “fat-burning zone”
Zone 2 does burn the highest percentage of its calories from fat, but harder zones burn more calories in total. For fat loss, what matters is the weekly calorie total you can sustain — and Zone 2's real advantage is that you can do a lot of it without wrecking recovery. Set your intake with the calorie calculator and let training quality follow.
Frequently asked questions
My watch says a different max HR — which is right?
If you have seen a genuine peak in a hard finish sprint, trust that number over any formula and enter zones from it. Formulas carry a ±10 bpm margin either way.
Is a high resting heart rate bad?
Above about 80 at true rest is worth mentioning to a doctor, though stress, caffeine and poor sleep all push it up. Falling resting HR over months is one of the clearest signs your training is working.
Do I need a chest strap?
Wrist sensors are fine for steady Zone 2 work and lag badly during intervals. For Zone 4–5 sessions a chest strap is noticeably more truthful.