Heart Rate Zone Calculator

How Heart Rate Zones Work

Heart rate training zones divide your effort range into five intensity bands, each targeting a different physiological adaptation. They're based on percentages of your maximum heart rate (MHR) — the fastest your heart can beat during all-out exertion.

Zone 1 — Recovery (50–60% MHR): Very light effort. Walking, gentle cycling, or post-workout cool-downs. This zone promotes blood flow for recovery without adding training stress. It's where you should spend most of your warm-up and cool-down time.

Zone 2 — Fat Burn / Aerobic Base (60–70% MHR): Comfortable conversational pace. Long runs, easy rides, and steady-state cardio live here. This zone builds your aerobic foundation and is where your body oxidizes the highest proportion of fat relative to carbohydrate. Endurance athletes spend 70–80% of their total training volume in Zone 2.

Zone 3 — Aerobic / Tempo (70–80% MHR): Moderate-to-hard effort. You can speak in short sentences but not hold a full conversation. Tempo runs and sustained efforts at marathon or half-marathon pace fall in this zone. It improves cardiovascular efficiency and lactate clearance.

Zone 4 — Threshold (80–90% MHR): Hard effort at or near your lactate threshold — the point where lactate accumulates faster than your body can clear it. Sustained intervals of 10–30 minutes at this intensity improve your ability to hold a fast pace. This is the zone that most directly predicts race performance.

Zone 5 — VO2 Max (90–100% MHR): Maximum effort. Short intervals of 30 seconds to 5 minutes at near-maximal intensity. Sprints, HIIT, and VO2 max intervals live here. This zone drives the highest cardiovascular adaptations per unit of time but also produces the most fatigue and recovery demand.

Max HR Formulas Compared

No estimation formula is perfectly accurate — all have a standard deviation of ±10–12 bpm. That means your true max heart rate could be up to 12 beats higher or lower than any formula predicts. If your zones feel off, a measured max HR from a graded exercise test or a field test is always more reliable than estimation.

Fox (1971): 220 − age. The original and most widely cited formula. It was derived from a literature review of 11 studies — not a single rigorous dataset — and tends to overestimate max HR in younger adults and underestimate it in older adults. Despite its limitations, it remains the default in most gym equipment and fitness apps because of its simplicity.

Tanaka (2001): 208 − 0.7 × age. Published in the Journal of the American College of Cardiology, this formula was derived from a meta-analysis of 351 studies involving 18,712 subjects. It corrects the age-related bias in the Fox formula and is generally considered the most accurate population-level estimate. This calculator uses Tanaka as the default.

Gulati (2010): 206 − 0.88 × age. Derived from a cohort of 5,437 asymptomatic women in the St. James Women Take Heart project. Because the Fox and Tanaka formulas were derived primarily from male subjects, Gulati provides a better fit for women — particularly women over 50. If you're a woman, try both Tanaka and Gulati and see which aligns better with your perceived exertion.

The practical difference between formulas is typically 3–8 bpm depending on age. At age 30, Fox gives 190, Tanaka gives 187, and Gulati gives 180. At age 60, Fox gives 160, Tanaka gives 166, and Gulati gives 153. The divergence grows with age, which is exactly why Tanaka and Gulati were developed — to correct the Fox formula's known bias at the extremes.

Karvonen vs. Simple Percentage

There are two common methods for calculating heart rate training zones, and this calculator supports both.

Simple % of Max HR multiplies your estimated max heart rate by the zone boundaries. Zone 2 at 60–70% of a 190 max HR gives 114–133 bpm. This method is straightforward and works reasonably well for most recreational exercisers.

The Karvonen method uses your heart rate reserve (HRR) — the difference between your max HR and resting HR — to set zone boundaries. The formula is: target HR = (HRR × intensity) + resting HR. For a person with a 190 max HR and 60 bpm resting HR, HRR is 130. Zone 2 becomes (130 × 0.60) + 60 = 138 bpm at the low end and (130 × 0.70) + 60 = 151 bpm at the high end — noticeably higher than the simple percentage method.

The Karvonen method is recommended by the American College of Sports Medicine (ACSM) because it accounts for individual fitness. A well-trained athlete with a resting HR of 45 bpm has a much larger heart rate reserve than an untrained person at 80 bpm — even if they share the same max HR. The Karvonen method reflects this by pushing the trained athlete's zones higher, which matches the real-world observation that fit individuals need to work harder to reach the same relative intensity.

To use the Karvonen method, enter your resting heart rate in the field above. If left blank, the calculator defaults to the simpler % of max HR approach.

The Fat Burn Zone Myth

Cardio machines and fitness trackers love to highlight the "fat burn zone" — typically Zone 2, around 60–70% of max HR. The claim is that exercising at this intensity burns the most fat. This is technically true as a percentage of fuel mix, but misleading as a fat loss strategy.

At low intensities, your body does derive a higher percentage of its energy from fat oxidation (roughly 60% fat, 40% carbohydrate). At high intensities, the ratio flips — more carbohydrate, less fat. But here's the catch: higher intensities burn dramatically more total calories per minute. If you burn 300 calories in 30 minutes at Zone 4, with 30% from fat, that's 90 calories of fat. If you burn 150 calories in 30 minutes at Zone 2, with 60% from fat, that's also 90 calories of fat — but you burned half the total calories in the same time.

For fat loss, what matters most is your total calorie deficit over time — not the fuel source during any single workout. Higher-intensity training also produces a greater afterburn effect (excess post-exercise oxygen consumption, or EPOC), which further increases total calorie expenditure in the hours following exercise.

That said, Zone 2 training is valuable for other reasons: it builds aerobic base, improves mitochondrial density, teaches your body to oxidize fat efficiently at higher absolute workloads, and generates far less fatigue than high-intensity work. Elite endurance athletes spend the majority of their training time in Zone 2 — not because it's a shortcut to leanness, but because it's the foundation of aerobic performance. The best approach for most people is a mix: 80% of sessions in Zones 1–2, and 20% at Zone 4 and above.

Frequently Asked Questions