How are heart rate training zones calculated?

First the tool estimates your maximum heart rate from your age. With the % of Max method, each zone is simply a percentage band of that maximum (Zone 1 is 50-60%, Zone 5 is 90-100%). With the Karvonen method it works from your heart-rate reserve instead, so it factors in your resting pulse for a more individual result.

What is the Karvonen formula?

The Karvonen formula uses your heart-rate reserve, which is maximum HR minus resting HR. A target is found with: target = resting HR + intensity x (max HR - resting HR). Because it accounts for your resting pulse, two people of the same age but different fitness get different target zones.

Which max heart rate formula should I use?

The classic 220 minus age (Fox) is easy to remember but overestimates for older adults and underestimates for some younger ones. The Tanaka equation, 208 minus 0.7 x age, is more accurate across ages. Gulati, 206 minus 0.88 x age, was derived specifically for women. A measured max from a lab or field test always beats any formula.

What is Zone 2 and why is it popular?

Zone 2 sits at roughly 60-70% intensity — an easy, conversational pace you can hold for a long time. It builds aerobic base, improves fat metabolism and mitochondrial density, and carries low injury and recovery cost, which is why endurance coaches prescribe large volumes of it.

Do I need a resting heart rate to use this?

Only for the Karvonen method. For % of Max HR you just need your age. To measure resting HR, count your pulse for 60 seconds first thing in the morning before getting out of bed, ideally averaged over a few days.

Are these zones medical advice?

No. They are estimates based on population-average formulas and are meant for general fitness planning. If you have a heart condition, are on medication that affects heart rate (such as beta-blockers), or are new to intense exercise, talk to a doctor before training by heart rate.

Heart Rate Zone Calculator

A heart rate zone calculator turns two simple inputs — your age and, optionally, your resting pulse — into five personalised training zones, each with an exact beats-per-minute (BPM) range. Whether you run, cycle, row or lift, training by heart rate keeps each session at the intensity that produces the result you actually want, instead of guessing from feel alone. This tool is for anyone with a fitness watch or chest strap who wants to know what number to aim for during an easy recovery jog versus a hard threshold interval.

How it works

Everything starts with your maximum heart rate (HRmax) — the highest your heart can beat in all-out effort. Because measuring it directly requires a maximal test, the calculator estimates it from your age using one of three published equations: the classic Fox formula (220 - age), the more accurate Tanaka equation (208 - 0.7 x age), or the Gulati equation (206 - 0.88 x age) derived for women. If you have a lab- or field-measured max, enter it as a custom value and skip the estimate entirely.

From HRmax the tool builds the five zones in one of two ways. The simple % of Max HR method takes fixed percentage bands of your maximum: Zone 1 is 50-60%, Zone 2 is 60-70%, and so on up to Zone 5 at 90-100%. The Karvonen method is more individual — it works from your heart-rate reserve (HRmax minus resting HR) and adds your resting pulse back in, so a fitter person with a low resting heart rate gets higher, more realistic targets. Each zone trains something different: recovery and aerobic base at the bottom, lactate threshold and VO2 max at the top. The calculator also shows a rough calorie-burn cue at a tempo effort, using the Keytel energy-expenditure equation, so you can sense the metabolic cost of a session at a glance. Every figure is computed instantly in your browser as you type — nothing is sent anywhere.

Worked example

Suppose you are 40 years old with a resting heart rate of 55 bpm, using the Tanaka formula and the Karvonen method. Your estimated max is 208 - 0.7 x 40 = 180 bpm, and your heart-rate reserve is 180 - 55 = 125 bpm. Zone 2 (60-70% of reserve) then becomes 55 + 0.60 x 125 = 130 up to 55 + 0.70 x 125 = 142 bpm. Zone 4 threshold work (80-90%) lands at roughly 155-168 bpm. Switch to the % of Max method and Zone 2 instead reads 108-126 bpm — lower, because it ignores your resting pulse. Both are valid; Karvonen is usually closer to how trained athletes actually feel.

Formula note. % of Max: target = intensity x HRmax. Karvonen: target = HRrest + intensity x (HRmax - HRrest), where intensity is the zone fraction (0.50 to 1.00) and HRmax comes from your chosen age equation or custom measured value.

These numbers are estimates from population-average equations and should be treated as a starting point, not a prescription. Individual maximum heart rates vary by 10-20 bpm from any formula, so refine your zones over time against how the efforts actually feel and perform.