Free running calculator

Heart Rate Zone Calculator

Work out a five-zone heart-rate guide using your known maximum heart rate, Heart Rate Reserve, or an age-based estimate.

% Max HRHeart Rate ReserveAge estimate5 training zones

Where do these calculations come from?

There is no single heart-rate-zone formula that is perfect for every runner. The methods below come from different ways of estimating exercise intensity, and they use different information about you.

Percentage of Maximum Heart Rate

This is the simplest method. Your training zones are set as percentages of your maximum heart rate. It works best when your maximum heart rate comes from a reliable test or a genuine hard effort rather than an age estimate.

Heart Rate Reserve — Karvonen

This method is associated with the work of Martti Karvonen, Elma Kentala and Olli Mustala, published in 1957. It uses both maximum heart rate and resting heart rate, so it takes more of your individual heart-rate range into account.

Age-Based Estimate

The calculator offers the traditional 220 − age rule and the newer 208 − (0.7 × age) equation published by Tanaka, Monahan and Seals in 2001. The Tanaka equation was developed from a large analysis of healthy adults, but both methods are still estimates rather than measurements of your own maximum heart rate.

Why can the answers be different? Each method starts with different information. % Max HR uses your maximum heart rate; Heart Rate Reserve uses both maximum and resting heart rate; age formulas first estimate your maximum from population averages. Because the starting point is different, the bpm boundaries can be different too. If you have a reliable measured maximum and resting heart rate, those usually give a more individual starting point than age alone.

Sources: Karvonen MJ, Kentala E, Mustala O. The effects of training on heart rate; a longitudinal study (1957). Tanaka H, Monahan KD, Seals DR. Age-predicted maximal heart rate revisited, Journal of the American College of Cardiology (2001).

Which calculation should I use?

Percentage of Max HR

Best when you already have a reasonably reliable personal maximum heart rate. Each zone is calculated directly as a percentage of that maximum.

Heart Rate Reserve

Uses both maximum and resting heart rate, making the calculation more individual than using maximum heart rate alone.

Estimate from Age

Useful as a starting point if you do not know your maximum heart rate, but an individual runner can be above or below an age-predicted value.

Choose your method

Use the best information you have. A measured maximum heart rate is more individual than an age estimate.

Heart rate is a guide, not a target to force. Heat, fatigue, dehydration, stress, caffeine, medication, hills and sensor accuracy can all affect the number you see.

Your heart rate zones

This uses a simple five-zone model. The percentages stay the same so you can see how the chosen calculation method changes the bpm ranges.

Zone	Intensity	Heart rate	How it should feel	Typical use
Calculate your details to fill the zone guide.

How the methods are calculated

Percentage of maximum heart rate

Zone boundary = Maximum HR × intensity %

Heart Rate Reserve (Karvonen)

Heart Rate Reserve = Maximum HR − Resting HR Target HR = Resting HR + (Heart Rate Reserve × intensity %)

Age estimate

208 − (0.7 × age) OR 220 − age

Important: Age-based maximum-heart-rate formulas are estimates, not precise predictions for an individual. Zone systems also differ between watches, apps and coaches. Use heart rate alongside pace, breathing, the talk test and how the run actually feels. If you have a heart condition, concerning symptoms, or have been advised to limit exercise intensity, follow medical guidance rather than a generic calculator.