Heart rate zones calculator

How the calculator works

It starts with your maximum heart rate, the fastest your heart can beat. If you do not know yours, it guesses from your age with the Tanaka formula: 208 minus 0.7 times your age. For someone aged 45, that comes to about 177 beats a minute (bpm).

Then it splits your maximum into five zones. Zone 1 is 50 to 60% of it, zone 2 is 60 to 70%, and so on up to zone 5 at 90 to 100%.

Tanaka or 220 minus age

The rule most people know is 220 minus your age. It is older and simpler. A 2001 study that pooled results from over 18,000 people found that 208 minus 0.7 times your age fits people better. It also found the old rule guesses too low for older adults. The calculator uses the newer formula and shows the older one as well.

Both are only a guess. Your own maximum may be quite a bit higher or lower.

Adding your resting heart rate

Your resting heart rate is how fast your heart beats when you are still. If you add it, the calculator uses the Karvonen method. It takes the gap between your resting and maximum heart rate, called your heart rate reserve. Each zone is the same share of that gap, added on top of your resting rate. Garmin watches can set zones this way too.

This method gives higher numbers, most of all in the easy zones.

A note on safety

If you have a heart condition, or take medicine that changes your heart rate, ask your doctor before you train by heart rate.

Where the numbers come from

• The Tanaka formula is from Tanaka, Monahan and Seals, Age-predicted maximal heart rate revisited (2001). The same paper names 220 minus age as the rule in common use.
• The five zones are from Polar and the Garmin Forerunner 945 manual. How each zone feels follows Bupa UK.
• The Karvonen method is from Karvonen, Kentala and Mustala, The effects of training on heart rate (1957).