Heart Rate Calculator
Calculate your max heart rate, training zones and VO2 max estimate
Fox formula: 220 − age. The most widely known formula, though it tends to overestimate for older adults.
Results & Details
// 5 Training Zones (% of Max HR)
// Check Any Heart Rate
// Karvonen Method (Heart Rate Reserve)
The Karvonen method uses your resting HR to give more personalised zones, accounting for individual fitness level.
// Max HR Formula Comparison
// VO2 Max Fitness Category
Understanding Heart Rate Training Zones
Heart rate training zones allow you to target specific physiological adaptations during exercise. Training at the right intensity for the right purpose is more effective than training hard all the time.
Formulas
The 5 Training Zones
Zone 1 — Recovery (50–60%): Very light effort. Used for warm-up, cool-down and active recovery. Improves basic endurance and fat metabolism.
Zone 2 — Aerobic (60–70%): Light to moderate effort. The most important zone for building aerobic base. Comfortable, conversational pace. Most of your training volume should be here.
Zone 3 — Tempo (70–80%): Moderate to hard. Improves aerobic capacity and efficiency. Somewhat uncomfortable but sustainable. Often overused by amateur athletes.
Zone 4 — Threshold (80–90%): Hard effort. Raises lactate threshold — the point at which lactic acid accumulates faster than it can be cleared. Used for interval training.
Zone 5 — VO2 Max (90–100%): Maximal effort. Improves maximum oxygen uptake. Only sustainable for short bursts. Used in sprint and high-intensity interval training.
What Is the Karvonen Method?
The Karvonen method calculates zones relative to your Heart Rate Reserve (max HR minus resting HR) rather than max HR alone. This produces more personalised zones because it accounts for individual fitness level — a fitter person with a lower resting HR will have higher target zones than a less fit person of the same age with the same max HR.
Heart Rate Zones: The Science and Its Error Bars
Built and verified by Andrius R. · Updated June 2026
Heart rate zones turn one number — beats per minute — into a training compass. They're genuinely useful, but they're built on an estimated maximum that can be off by 10+ beats, so it pays to know both the system and its limits.
Estimating max heart rate (and how wrong it can be)
The famous 220 − age formula gives a 40-year-old a max of 180 bpm; the better-validated Tanaka formula (208 − 0.7 × age) happens to also give 180 at age 40 — the two diverge mostly for younger and older people. The honest caveat: both carry a standard deviation of ~10–12 bpm, meaning a real 40-year-old's max could easily be 168 or 192. Genetics dominates; fitness barely changes your max (training changes what you can sustain, not the ceiling). If zones matter to you, calibrate: the highest value you see at the end of an all-out hill-sprint session or hard race beats any formula.
The five zones, with real numbers
| Zone | % of max | BPM | What it's for |
|---|---|---|---|
| Z1 — Recovery | 50–60% | 90–108 | Warm-up, active recovery |
| Z2 — Easy/aerobic | 60–70% | 108–126 | The base-building workhorse; conversational |
| Z3 — Moderate | 70–80% | 126–144 | Steady "comfortably hard" efforts |
| Z4 — Threshold | 80–90% | 144–162 | Tempo work; raises sustainable pace |
| Z5 — Maximal | 90–100% | 162–180 | Short intervals; VO₂ max development |
The Karvonen upgrade: using your resting heart rate
Percent-of-max zones ignore individual fitness. The Karvonen method fixes this by working with heart rate reserve (max − resting): target = resting + %intensity × reserve. Our 40-year-old with a resting HR of 60 has a reserve of 120, putting Karvonen Zone 2 at 132–144 bpm — notably higher than the simple method's 108–126. For people with low resting heart rates the simple zones run too easy; if you know your resting HR (measure it on waking), Karvonen is worth the extra arithmetic, and this calculator supports it.
Why so much training belongs in Zone 2
Endurance sport converged on a roughly 80/20 split — most volume easy (Z1–Z2), a sliver hard (Z4–Z5) — because easy work drives the deep aerobic adaptations (mitochondria, capillaries, fat metabolism, stroke volume) while staying recoverable day after day. The common failure mode is the "moderate-intensity rut": every session drifting into Z3, too hard to recover from quickly, too easy to force top-end adaptation. If your easy days don't feel almost too easy, they're not easy days.
When the numbers lie
Heart rate lags effort by 1–2 minutes (useless for judging short sprints — use pace or power there), drifts upward over long sessions even at constant effort ("cardiac drift"), and rises with heat, dehydration, caffeine, stress and poor sleep. Wrist-based optical sensors also misread during high-cadence or cold conditions; a chest strap is meaningfully more accurate. And an elevated resting heart rate for several days is one of the more reliable cheap signals of accumulating fatigue or oncoming illness — the same number, used as a recovery gauge. Medications (notably beta-blockers) change everything above; zones for medicated athletes need a clinician's input, not a formula.
From the Blog
// 80/20 Rule
Elite endurance athletes spend ~80% of training in Zone 1–2 and only ~20% in Zones 3–5. Most amateurs do the opposite.
// Resting HR
Measure resting HR first thing in the morning before getting up. Under 60 bpm indicates good cardiovascular fitness.
// Zone 2 Benefits
Consistent Zone 2 training improves mitochondrial density and fat oxidation — the foundation of endurance performance.
// Overtraining
A resting HR 5–7 bpm higher than normal is an early sign of overtraining or illness. Take an easy day.