Target Heart Rate Zone Calculator
Heart rate zones turn effort into numbers: five bands from easy recovery up to maximal work, each training a different quality. This calculator builds your zones from age using the Tanaka formula, and personalizes them with the Karvonen reserve method when you add your resting heart rate.
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How it's calculated
Step one is predicting your maximum heart rate with the Tanaka formula: 208 − 0.7 × age. Tanaka's 2001 meta-analysis of over 18,000 subjects showed it outperforms the traditional '220 minus age' rule, which increasingly underestimates max heart rate with age. A 40-year-old gets a predicted max of 180 bpm.
With max HR alone, the five zones are simple percentage bands of maximum: Zone 1 recovery (50-60%), Zone 2 aerobic base (60-70%), Zone 3 tempo (70-80%), Zone 4 threshold (80-90%), and Zone 5 maximal (90-100%). Add your resting heart rate and the calculator upgrades to the Karvonen method: target HR = resting HR + %intensity × (max HR − resting HR). Karvonen anchors zones to your heart rate reserve — the usable span between rest and max — which matters because a trained 40-year-old resting at 48 bpm and an untrained one resting at 78 bpm have very different working ranges that plain percent-of-max ignores.
The zone doing the most work in most programs is Zone 2: conversational-pace aerobic training that builds mitochondrial density and fat oxidation, and should form the bulk of endurance volume. Zone 4 near threshold raises the pace you can sustain; Zone 5 intervals push VO2 max. The classic error is living in Zone 3 — too hard to recover from easily, too easy to force adaptation. Two honest caveats: age-predicted max HR carries an individual spread of roughly ±10 bpm, and beta-blockers or similar medication shift heart rate enough that zones should come from observed values instead.
Frequently asked questions
What heart rate zone burns the most fat?
Zone 2 (60-70% of max) burns the highest share of calories from fat and builds aerobic base — but total calories, not the fuel mix during exercise, decide fat loss.
Why add resting heart rate to the calculation?
It switches the math to the Karvonen reserve method, anchoring zones to your span between resting and max HR — noticeably more personal for trained or detrained people.
How accurate is an age-predicted max heart rate?
The Tanaka formula is the best population estimate but individuals spread about ±10 bpm around it. A field test or observed race max beats any formula.
How much training should be Zone 2?
For endurance-focused training, roughly 70-80% of weekly volume. Most self-coached athletes drift into Zone 3 — keep easy days genuinely easy.
Take it with you
Every calculator, plus workout and macro tracking, in the ElevenSix Fitness app for iPhone.