Fat Burning Zone Calculator

Background.

The fat-burning zone rests on a real observation that is often stretched too far. At easy and moderate effort your muscles draw a larger share of their fuel from fat; as you push harder, carbohydrate takes over. What the idea leaves out is that total energy use climbs with intensity, so a harder session can burn as much fat in absolute terms and more calories overall. For weight loss, the calories spent across a week matter far more than the fuel mix of any one workout. The zone is better thought of as a steady aerobic pace you can hold for a long time and repeat often.

To turn that pace into a pulse to watch, the page combines two published methods. Maximum heart rate is predicted from age with the Tanaka equation, 208 − 0.7 × age, from a 2001 meta-analysis in the Journal of the American College of Cardiology. The Karvonen method then works on heart-rate reserve, the gap between that maximum and your resting pulse, adding the chosen share of it back on top of the resting rate. A fit person with a low resting rate has a wide reserve, so the zone fits them in a way that plain percent-of-maximum does not.

The difference is large. For a 35-year-old with a resting pulse of 60, 60–70% of heart-rate reserve is 134 to 146 beats per minute, while 60–70% of maximum would be only 110 to 128. Many charts mix the two without saying which they mean.

Treat the numbers as a starting point. The age prediction can be off by 10 beats a minute or more for an individual, and beta-blockers, heat, dehydration and illness all shift heart rate in ways the formulas ignore.

What is fat burning zone calculator?

The fat-burning zone is a target heart-rate range for steady aerobic exercise. Here it is set as a percentage of heart-rate reserve, the number of beats between your resting pulse and your predicted maximum, so 0% corresponds to resting and 100% to an all-out effort. The default band of 60–70% of reserve sits at the lower edge of what the American College of Sports Medicine calls vigorous; its moderate band is 40–59%. The results are beats per minute you can read from a watch or chest strap.

How to use this calculator.

1. 01Enter your age in years; the page accepts ages from 13 to 100.
2. 02Measure your resting heart rate on waking, before you get out of bed, by counting your pulse for a full minute or reading a wearable's overnight figure. Averaging three mornings smooths out a poor night's sleep or a late coffee.
3. 03Set the lower and upper intensity as percentages of heart-rate reserve. The defaults of 60 and 70 give a steady aerobic band; 40 and 59 give a gentler, conversational one. The upper figure must be higher than the lower.
4. 04Read the two target heart rates and the predicted maximum beside them. The page always uses the age prediction, so if you have a maximum measured in a supervised exercise test, your true zone may sit higher or lower.

The formula.

There are two steps. First, maximum heart rate is estimated as HRmax = 208 − 0.7 × age, the Tanaka equation. It was proposed because the older 220 − age rule underestimates the maximum in older adults: the two agree at age 40, where both give 180 bpm, and part company after that, so a 60-year-old gets 166 from Tanaka against 160. Second, the Karvonen formula sets each end of the zone as target = resting HR + intensity × (HRmax − resting HR), with intensity written as a fraction, so 60% becomes 0.60. The bracketed term is the heart-rate reserve. A change in resting rate moves the targets by less than one beat per beat, because a higher resting rate also narrows the reserve. The resting rate must be below the predicted maximum for the zone to exist.

A worked example.

Frequently asked questions.

References& sources.

1. [1]Tanaka, Monahan and Seals. Journal of the American College of Cardiology 2001. Age-predicted maximal heart rate meta-analysis. Retrieved 2026-08-06.
2. [2]U.S. National Library of Medicine. PubMed record current 2026-08-06. Indexed derivation and validation literature. Retrieved 2026-08-06.
3. [3]World Health Organization. Patient safety resources current 2026. Clinical decision-support safety context. Retrieved 2026-08-06.