Running Heart Rate Zones Calculator — Max HR, Karvonen & MAF 180

Find your five training zones with the method that fits how you train — Max HR, the Karvonen heart-rate-reserve method, or Phil Maffetone's MAF 180. Bookmark it; re-check whenever your fitness or watch changes.

The three methods explained

1. Max HR (percentage of maximum)

The simplest method. Your zones are straight percentages of your maximum heart rate. If you don't know your true max, we estimate it with the Tanaka formula (208 − 0.7 × age), which is more accurate than the old "220 − age" for most adults. Enter your real measured max if you have one — it's worth it.

2. Karvonen (heart-rate reserve)

The gold standard for individualisation. It uses your heart-rate reserve — the gap between resting and max HR — so a fit runner with a low resting pulse gets zones tuned to them. Target HR = % × (Max − Rest) + Rest. You'll need a reliable resting heart rate (measure it first thing in the morning).

3. MAF 180 (Maffetone)

Popular with low-heart-rate and ultra runners. Your maximum aerobic ceiling is 180 − age, adjusted up or down for fitness and health. Train at or just below this number to build a huge aerobic base while staying fat-burning and injury-resistant. It's a ceiling, not a target to push against.

Keep your easy runs in Zone 2 and the long runs in your sub-4 plan will pay off far more. Most runners go too hard on easy days and too easy on hard days.

Which heart rate method should I use?

If you know your resting HR, use Karvonen — it's the most personalised. If you're building a base or coming back from injury, try MAF 180. Otherwise the simple Max HR percentages are perfectly good for everyday training.

How do I find my true max heart rate?

A formula is only an estimate. To measure it, do a hard progressive effort (e.g. several uphill repeats after a thorough warm-up) and read the highest number your monitor shows — or do a supervised test. Enter that value for the most accurate zones.

What is Zone 2 and why does everyone talk about it?

Zone 2 is comfortable, conversational running — roughly 60–70% of max HR. It builds aerobic fitness, mitochondria and fat-burning with low injury risk, which is why endurance coaches want the bulk of your weekly volume there.