Heart Rate Zones: Percent of Max vs Heart Rate Reserve

What the five zones mean

The most common scheme uses five bands, each a slice of your maximum heart rate. Coaches, apps and books draw the lines a little differently, so treat the labels as a guide rather than a standard.

Estimating your maximum heart rate

Everything starts with a maximum. The best measure is an actual maximal effort, but that is hard work and not appropriate for everyone, so most people use a formula. Two are widely quoted:

max = 220 − ageThe older, simpler formula.

max = 208 − 0.7 × ageThe Tanaka formula. Both are averages across groups of people, not predictions for one person.

The two agree around age 40 and drift apart at the extremes. Individual maximums can sit 10 beats or more away from either formula, and fitness does not raise your maximum much, so a very fit person can easily be above or below the estimate.

Formulas can also produce decimals. For a 55-year-old, the Tanaka formula gives 208 − 0.7 × 55 = 208 − 38.5 = 169.5, which you would round to 170 bpm, while 220 − 55 gives 165. A five-beat difference moves every zone boundary, which is a good reason to treat zones as bands rather than exact lines.

Method 1: percent of maximum

Multiply your maximum by each percentage. Worked example: a 40-year-old with an estimated maximum of 180 beats per minute (bpm).

This method needs only your age, which is why most devices default to it. Its weakness is that it ignores how fast your heart beats at rest.

Method 2: heart rate reserve (Karvonen)

Heart rate reserve is the gap between your resting and maximum rates, and the Karvonen method builds each target on top of your resting heart rate.

Measure resting heart rate first thing in the morning, before getting up or having coffee. Count your pulse for a full 60 seconds, or use the lowest steady reading from a wearable, and average several mornings, because single readings vary by a few beats. Adults at rest are usually in the range of 60 to 100 bpm, and people who train regularly are often lower.

target = resting + (max − resting) × intensityIntensity is written as a decimal, so 70% is 0.70.

Worked example: the same 40-year-old has a resting rate of 60 bpm. The reserve is 180 − 60 = 120. At 70% intensity, the target is 60 + 120 × 0.70 = 144 bpm. The percent-of-max method gives 0.70 × 180 = 126 bpm for the same 70%.

The numbers differ because the percentages mean different things: 70% of reserve is a harder effort than 70% of maximum. In this example it is 144 bpm, which is 80% of the 180 bpm maximum, while 126 bpm is 70% of maximum. Do not mix them. If a plan says "70% of heart rate reserve", use the Karvonen formula, and if it says "70% of max", use the first table.

Using zones sensibly

A common way to use the bands is to spend most sessions in zones 1 to 3, where the effort is sustainable for a long time, and keep zones 4 and 5 for short, structured efforts such as intervals, with easier days in between. Neither calculation method tells you which zone you should train in. That depends on your goal, your fitness and how much recovery you get.

• Cross-check with the talk test. If your heart rate says "easy" but you cannot speak in full sentences, trust your breathing and adjust.
• Expect day-to-day drift. Heat, caffeine, poor sleep, illness and dehydration can all raise your heart rate for the same effort.
• Mind the sensor. Wrist-based optical sensors can lag or misread during intervals; a chest strap is generally more reliable for hard sessions.
• Update your numbers. Recheck your resting rate every few weeks and your age-based maximum each year.

To get all five bands for your own age and resting rate in seconds, use the target heart rate calculator.

This article is general education, not medical advice. If you have a heart condition, take medication that affects heart rate, or are new to vigorous exercise, check with a doctor before training at high intensities.