Heart Rate Zone Calculator

About the Heart Rate Zone Calculator

Heart rate zones turn a vague instruction like "go easy" or "push hard" into a number you can see on a watch. Most sports watches, fitness apps and training plans use a five-zone model, from very light recovery work in zone 1 to all-out efforts in zone 5. Training in the right zone makes easy days genuinely easy, hard days genuinely hard, and helps you build endurance without constant fatigue.

This heart rate zone calculator works out all five zones in beats per minute. It estimates your maximum heart rate from your age with the Tanaka or Fox formula — or uses a maximum you have measured — and sets the zones either as a straight percentage of maximum or with the Karvonen method, which uses your resting heart rate to reflect your fitness.

How to Use the Heart Rate Zone Calculator

Enter your age and choose the formula for maximum heart rate, or enter a measured maximum if you know it.

Choose percent of maximum or Karvonen.

For Karvonen, enter your resting heart rate, measured first thing in the morning before getting up.

The Formulas

  maximum heart rate (Tanaka)  = 208 − 0.7 × age
  maximum heart rate (Fox)     = 220 − age

  percent of max:  zone limit = maximum × percentage
  Karvonen:        zone limit = resting + percentage × (maximum − resting)

  Zone 1  50–60%     Zone 2  60–70%     Zone 3  70–80%
  Zone 4  80–90%     Zone 5  90–100%

Step-by-Step Examples

A 40-year-old, percent of maximum.

  maximum   208 − 0.7 × 40 = 180 bpm

  Zone 1    90–108 bpm
  Zone 2   108–126 bpm
  Zone 3   126–144 bpm
  Zone 4   144–162 bpm
  Zone 5   162–180 bpm

The same person with the Karvonen method and a resting rate of 60.

  reserve   180 − 60 = 120 bpm
  Zone 2    60 + 0.6 × 120 = 132  to  60 + 0.7 × 120 = 144 bpm
  Zone 5    60 + 0.9 × 120 = 168  to  180 bpm

The Karvonen zones sit higher because the resting rate is added back to each one.

What Each Zone Is For

Zone 1 (50–60%) is very light: warm-ups, cool-downs and recovery sessions.

Zone 2 (60–70%) is easy, conversational effort. It builds the aerobic base — more capillaries, more mitochondria, better fat use — and is where many endurance athletes spend most of their training time.

Zone 3 (70–80%) is moderate, steady work: comfortably hard, with speech in short sentences.

Zone 4 (80–90%) is hard, around the lactate threshold. It raises the pace you can hold in races from 10 km to the half marathon.

Zone 5 (90–100%) is maximal: short intervals and sprints that you can only sustain for a minute or a few minutes.

Which Maximum Heart Rate Formula?

220 − age is the most famous formula, but it was never derived from a proper study. Tanaka's 208 − 0.7 × age, from a large analysis of hundreds of studies, fits real data better. The two agree at exactly 40; below 40, Fox gives a higher maximum (190 bpm at 30, against 187 for Tanaka), and above 40 a lower one. Either way, individuals can differ from any age formula by 10 bpm or more, so a measured maximum — from a hard hill-repeat session or a laboratory test — gives more accurate zones.

Percent of Max or Karvonen?

The percent of maximum method is simple and matches most watches' default settings. The Karvonen method uses your heart rate reserve, the gap between resting and maximum, which narrows or widens with fitness. Two people with the same maximum but resting rates of 50 and 75 get different Karvonen zones, as they should. Because Karvonen adds the resting rate back, its zones are always higher than percent-of-max zones at the same percentage, so do not mix the two systems when following a plan.

The 80/20 Approach

Many endurance coaches recommend spending roughly 80 percent of training time at low intensity — zones 1 and 2 — and about 20 percent at moderate to high intensity. This pattern, seen in many elite endurance athletes, lets you train often without accumulating too much fatigue. A common mistake among recreational runners and cyclists is doing most sessions in zone 3: too hard to recover from easily, but not hard enough to raise top-end fitness.

Heart Rate Drift and Other Quirks

Heart rate does not only reflect effort. On a long session at steady pace, it slowly rises — cardiac drift — as you warm up, lose fluid and tire. Heat, dehydration, caffeine, stress, illness and poor sleep all push heart rate up, while some medications, such as beta-blockers, hold it down. Optical sensors on watches can also misread during intervals or in cold weather. For these reasons, many coaches combine heart rate with pace, power and perceived effort rather than relying on any one of them alone. Comparing heart rate at the same pace from month to month is also a simple way to see fitness improving.

Understanding Your Result

The headline is the maximum heart rate used.

The zone lines give each zone's range in beats per minute, the percentage, and what the zone is used for.

The worth knowing line explains the limits of the method you chose.

When Should You Use This Calculator?

Use it to set up the heart rate zones on a watch or app.

Use it to follow a training plan written in zones.

Use it to check that easy sessions are really easy.

Use it to update your zones when your resting heart rate changes.

Common Mistakes

Trusting an age formula as exact. Individual maximums vary by 10 bpm or more.

Mixing methods. Karvonen zones are higher than percent-of-max zones.

Measuring resting heart rate after coffee or exercise. Take it on waking.

Running every session in zone 3. Keep easy days easy.

Ignoring heat and fatigue. Heart rate drifts up in hot weather and when tired.