Key Takeaways
- The fat burning zone is a heart rate range. This tool uses 60 to 80 percent of maximum heart rate, the range one study of 36 relatively fit runners said maximal fat burning can be assumed to fall in[1].
- It is a starting point, not your number. The average peak sat at 61.5 percent of maximum heart rate in 300 healthy adults[2], and in a 2023 test of 26 people the heart rate at measured peak fat burning did not line up with 50, 70 or 80 percent of predicted maximum[15].
- Maximum heart rate is the weak link. Published errors for the equations run from 7 to 11 beats[9], and the HUNT study reports 10.8[8]. This tool lets you compare three equations.
- Burning more fat during a session is not the same as losing more body fat. A 2021 review found no support for that link[5], and a 2023 meta-analysis found interval training worked as well or better[6].
- Beta blockers can keep your heart rate from reaching a standard target[19], and other medicines can lower maximum heart rate[10]. If that could be you, ask your doctor first. The talk test works without any number.
What the Fat Burning Zone Is
Your body burns a mix of fat and carbohydrate at every effort level. The amount of fat burned per minute rises with effort, peaks at a moderate pace, then falls as you go harder. Researchers call that peak maximal fat oxidation, or MFO[4].
Carey tested 36 relatively fit runners on a treadmill. Their personal fat burning zones averaged 67.6 to 87.1 percent of maximum heart rate, and varied a lot from runner to runner[1].
He also wrote that, without lab testing, you can assume MFO lies between 60.2 and 80 percent of maximum heart rate[1]. This calculator rounds that to 60 to 80.
Other studies point the same way. In 300 healthy adults the average peak was 48.3 percent of VO2max, which is 61.5 percent of maximum heart rate[2]. In 55 trained men it was 62.5 percent of VO2max, plus or minus 9.8[3].
The newest check I found is a 2023 study of 26 people. It compared each person's heart rate at measured peak fat burning with 50, 70 and 80 percent of predicted maximum. The two did not agree, with a mean difference of 23 beats a minute[15].
The authors recommended direct measurement instead.
What a calculator cannot do
Your own peak can only be found in a lab test that measures the gases you breathe out. This tool gives a published planning range. It cannot tell you where your peak sits, or whether it falls inside that range at all.
How the Fat Burning Zone Is Calculated
The main method has two steps. First get a maximum heart rate. Then take 60 and 80 percent of it.
Maximum heart rate = 220 − age
Bottom of zone = 60% × maximum
Top of zone = 80% × maximum
Worked example: age 35, resting heart rate 60
Maximum = 220 − 35 = 185
60% × 185 = 111
80% × 185 = 148
Zones are worked out from the rounded maximum and rounded to the nearest beat, halves up. That way you can check any result by hand.
The Karvonen method
The Karvonen method uses heart rate reserve, which is maximum minus resting. Karvonen and colleagues studied how training changes heart rate in 1957[14]. I could not read that paper online, so the formula here is the one commonly quoted.
Reserve = maximum − resting
Target = resting + percent × reserve
Same example with Karvonen
Reserve = 185 − 60 = 125
60%: 60 + 60% × 125 = 135
80%: 60 + 80% × 125 = 160
The Karvonen numbers sit higher. The research range was reported for percent of maximum heart rate, so I show Karvonen as a second convention, not as a fat burning result.
How to use the calculator
- Enter your age.
- Choose how to get your maximum heart rate: 220 minus age, Tanaka, HUNT, or a number you measured.
- Add your resting heart rate if you want the heart rate reserve (Karvonen) version too.
- Press the button, then read the zone in beats per minute.
- Check the zone by feel with the talk test.
Which Maximum Heart Rate Equation to Use
Every zone depends on the maximum you start from. The three equations below give different answers for the same person. At age 35 they range from 184 to 189.
| Equation | Built from | Age 35 |
|---|---|---|
| 220 − age | Not derived from original research, standard error of 7 to 11 beats[9] | 185 |
| 208 − 0.7 × age | Meta-analysis of 351 studies (18,712 people), checked in 514 healthy adults[7] | 184 |
| 211 − 0.64 × age | 3,320 healthy adults aged 19 to 89, standard error 10.8 beats[8] | 189 |
Three published equations for maximum heart rate, with the result at age 35
No equation wins. In a comparison against 99 graded treadmill tests, 220 minus age and Tanaka were not significantly off on average, the HUNT equation was, and all of them had wide limits of agreement. The authors suggested 220 minus age may be the best option for a general population[16].
I kept 220 minus age as the default for that reason, and because the American Heart Association chart uses it[10]. Switch to Tanaka or HUNT to see how much your zone moves. An expert quoted by Harvard Health says any age-based estimate can be off by as much as 15 beats[11].
If you know your real maximum
Choose "I know mine" and enter it. The Shookster authors advise using a graded exercise test to get maximum heart rate where you can[16]. That beats every equation here.
Fat Burning Heart Rate by Age
This chart uses 60 to 80 percent of maximum heart rate for healthy adults. Each column uses a different maximum heart rate equation, which is why they differ. Rows come from the same function as the calculator.
| Age | 220 − age | Tanaka | HUNT |
|---|---|---|---|
| 20 | 120 to 160 | 116 to 155 | 119 to 158 |
| 25 | 117 to 156 | 115 to 153 | 117 to 156 |
| 30 | 114 to 152 | 112 to 150 | 115 to 154 |
| 35 | 111 to 148 | 110 to 147 | 113 to 151 |
| 40 | 108 to 144 | 108 to 144 | 111 to 148 |
| 45 | 105 to 140 | 106 to 142 | 109 to 146 |
| 50 | 102 to 136 | 104 to 138 | 107 to 143 |
| 55 | 99 to 132 | 102 to 136 | 106 to 141 |
| 60 | 96 to 128 | 100 to 133 | 104 to 138 |
| 65 | 93 to 124 | 98 to 130 | 101 to 135 |
| 70 | 90 to 120 | 95 to 127 | 100 to 133 |
Fat burning heart rate in beats per minute, 60 to 80% of maximum, by age and equation
A chart cannot know your resting rate, your fitness or your medicines. Use it to sanity-check the calculator, not to replace it.
Does Staying in the Zone Burn More Body Fat?
Not necessarily. Burning more fat during a workout is a different thing from losing body fat over weeks. Harris and Kuo reviewed the idea in 2021 and noted that 24-hour fat oxidation did not change in the work they discuss[5].
They say this does not support a causal link between fat burning and fat loss. That paper is a review that offers another explanation. It is not a trial of zone training.
A 2023 meta-analysis of randomised trials compared high-intensity intervals with moderate steady exercise for fat loss in young and middle-aged adults. Intervals had a similar or better effect[6].
So the zone is a fair choice if you like steady, comfortable cardio. Nothing here says you must stay in it to lose fat. Pick the intensity you will repeat.
Check Your Zone With the Talk Test
Harvard Health gives a simple rule. If you are breathing faster than usual but can still hold a conversation, you are at moderate intensity. If finishing a sentence is hard, you are at vigorous intensity[11].
Mayo Clinic puts it the same way: at a moderate level you can talk but not sing[20].
The talk test has published support. One study looked at how consistent it is for exercise prescription[12]. A later review calls it a useful tool for prescribing and monitoring intensity[13].
It does not depend on an estimated maximum. Mayo suggests it, along with a perceived exertion scale, for people on beta blockers, and says that if you cannot talk while you exercise you are likely working too hard[19].
One limit: the talk test separates moderate from vigorous effort. I found no study that ties it to the peak of fat burning, so it checks your effort, not your fat burning.
Women, Older Adults and Medication
Sex: the Tanaka and HUNT studies both found no difference between men and women in how maximum heart rate falls with age[7][8]. This tool does not adjust for sex. Harvard Health quotes an expert who says 220 minus age tends to overestimate in women[11], so the sources disagree.
In 300 healthy adults the average peak came at a lower share of VO2max in men (45 percent) than in women (52 percent), with wide spread in both[2]. That does not change the band here.
Age: the equations were built on adults, and the HUNT sample ran from 19 to 89[22]. The calculator warns under 18 and above 89, and blocks ages below 10 and above 100.
Medicines and heart conditions
The American Heart Association notes that some medicines lower maximum heart rate[10].
Mayo Clinic says that on a beta blocker you might never reach your target heart rate however hard you exercise[19]. If you take one, or have a heart condition, ask your doctor for a target instead of using these numbers.
Fat Burning Zone vs Other Heart Rate Zones
The same maximum heart rate gives different numbers depending on whose bands you use. The table shows each one for a 40-year-old with a maximum of 180 (220 minus age).
| Band | % of max | Beats per minute |
|---|---|---|
| Fat burning range used hereCarey 2009 | 60 to 80 | 108 to 144 |
| AHA moderateAmerican Heart Association | 50 to 70 | 90 to 126 |
| AHA vigorousAmerican Heart Association | 70 to 85 | 126 to 153 |
| CDC moderateas Harvard Health quotes it | 64 to 76 | 115 to 137 |
| CDC vigorousas Harvard Health quotes it | 77 to 93 | 139 to 167 |
Heart rate bands at age 40, maximum 180 beats per minute
The AHA prints 50 to 70 and 70 to 85 percent[10][20]. Harvard Health and the Human Performance Resource Center quote the CDC at 64 to 76 and 77 to 93 percent[11][21]. I could not open a current CDC page that prints percentages, so the CDC rows are as those two sources quote them.
The 60 to 80 percent fat burning range overlaps the moderate and vigorous bands of both.
What This Calculator Leaves Out
Some fat burning calculators offer a Zoladz zone, which they describe as five bands centred 50, 40, 30, 20 and 10 beats under maximum, each plus or minus 5. I found no research that tests any of those bands as a fat burning zone, so there is no Zoladz result here.
Many charts also print a fat percentage for each zone, such as 85 percent fat at the lowest. I found no source for those numbers, so there is no fuel table here.
Fitness level is not an input. It changed no numbers in the calculator I replaced, and I found no sourced rule for how it should.
Frequently Asked Questions
Sources & References
- Quantifying differences in the "fat burning" zone and the aerobic zone: implications for training. Carey DG. Journal of Strength and Conditioning Research (2009)
- Determinants of fat oxidation during exercise in healthy men and women: a cross-sectional study. Venables MC, Achten J, Jeukendrup AE. Journal of Applied Physiology (2005)
- Maximal fat oxidation during exercise in trained men. Achten J, Jeukendrup AE. International Journal of Sports Medicine (2003)
- Understanding the factors that effect maximal fat oxidation. Purdom T, Kravitz L, Dokladny K, Mermier C. Journal of the International Society of Sports Nutrition (2018)
- Scientific Challenges on Theory of Fat Burning by Exercise. Harris MB, Kuo CH. Frontiers in Physiology (2021)
- Effect of High-Intensity Interval Training vs. Moderate-Intensity Continuous Training on Fat Loss and Cardiorespiratory Fitness in the Young and Middle-Aged: A Systematic Review and Meta-Analysis. Guo Z, Li M, Cai J, Gong W, Liu Y, Liu Z. International Journal of Environmental Research and Public Health (2023)
- Age-predicted maximal heart rate revisited. Tanaka H, Monahan KD, Seals DR. Journal of the American College of Cardiology (2001)
- Age-predicted maximal heart rate in healthy subjects: The HUNT fitness study. Nes BM, Janszky I, Wisløff U, Støylen A, Karlsen T. Scandinavian Journal of Medicine & Science in Sports (2013)
- The surprising history of the "HRmax=220-age" equation. Robergs RA, Landwehr R. Journal of Exercise Physiology online (2002)
- Target Heart Rates Chart (reviewed August 2024). American Heart Association (2024)
- All about your heart rate (CDC percentages are as Harvard Health quotes them). Harvard Health Publishing
- Consistency of the talk test for exercise prescription. Persinger R, Foster C, Gibson M, Fater DC, Porcari JP. Medicine & Science in Sports & Exercise (2004)
- The talk test: a useful tool for prescribing and monitoring exercise intensity. Reed JL, Pipe AL. Current Opinion in Cardiology (2014)
- The effects of training on heart rate; a longitudinal study (abstract not available online). Karvonen MJ, Kentala E, Mustala O. Annales Medicinae Experimentalis et Biologiae Fenniae (1957)
- Discrepancy between predicted and measured exercise intensity for eliciting the maximal rate of lipid oxidation. Kittrell HD, DiMenna FJ, Arad AD, Oh W, Hofer I, Walker RW, Loos RJF, Albu JB, Nadkarni GN. Nutrition, Metabolism and Cardiovascular Diseases (2023)
- Accuracy of Commonly Used Age-Predicted Maximal Heart Rate Equations. Shookster D, Lindsey B, Cortes N, Martin JR. International Journal of Exercise Science (2020)
- Zone 2 Intensity: A Critical Comparison of Individual Variability in Different Submaximal Exercise Intensity Boundaries (journal and year not confirmed). Meixner B, Filipas L, Holmberg HC, Sperlich B
- What Is “Zone 2 Training”?: Experts’ Viewpoint on Definition, Training Methods, and Expected Adaptations. Sitko S, et al.. International Journal of Sports Physiology and Performance (2025)
- Beta blockers: How do they affect exercise?. Mayo Clinic
- Exercise intensity: How to measure it. Mayo Clinic
- How to train using heart rate zones (quoted for the CDC percentages). Human Performance Resource Center
- HUNT heart rate formula: Maximal heart rate and age. NTNU, K.G. Jebsen Center for Exercise in Medicine (CERG)
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Disclaimer: This tool is for informational and personal journaling purposes only. Results are estimates based on published formulas and may vary based on individual factors such as genetics, training history, and measurement technique.