Fat Burning Zone Calculator
Find the heart-rate range where fat supplies the biggest share of your fuel. Enter your age (and resting heart rate in bpm if you choose the Karvonen method) to get your fat-burning zone, cardio zone, and estimated max heart rate.
Example: with Age 35 · Resting heart rate (bpm, Karvonen only) 65 · Method % of max heart rate (simple) → Fat-burning zone (60-70%): 111–130 bpm.
- Cardio zone (70-80%)130–148 bpm
- Estimated max heart rate (220 − age)185 bpm
Computed by the calculator below using its default values. Change any input to see your own numbers.
Max HR = 220 − age (Fox convention). Fat-burning zone = 60-70% of max HR, or 60-70% of heart-rate reserve added to resting HR (Karvonen).
What the fat-burning zone is — and is not
At easier intensities your muscles burn a higher percentage of fat; push harder and the mix shifts toward carbohydrate. The classic 'fat-burning zone' pins that easy band at 60-70% of maximum heart rate, with max HR estimated by the 220 − age convention (Fox, 1971). It is a real physiological effect — research on maximal fat oxidation finds the peak around moderate effort for most people — and it matches the comfortable 'zone 2' pace endurance athletes train at.
The catch: percentage is not total. Thirty minutes of harder cardio burns more total calories, and often more total fat, than thirty easy minutes. Use the zone for sustainable, long, conversational sessions — not because harder exercise somehow stops burning fat.
Simple percentage vs Karvonen
The simple method takes straight percentages of max HR. The Karvonen method works from heart-rate reserve — the span between resting and max — so a fitter person with a low resting pulse gets a higher, more personal target. Both inherit the weakness of 220 − age, which misses real max HR by 10+ bpm for about a third of people; if you know your true max from a test, anchor to that instead.
How it’s calculated
Max HR = 220 − age (Fox convention; Tanaka's 208 − 0.7×age is a common research alternative). Simple method: fat-burning zone = 60-70% of max HR; cardio zone = 70-80%. Karvonen method: zone = (max HR − resting HR) × percentage + resting HR, same 60-70% and 70-80% bands. Results rounded to whole bpm.
Age-predicted max HR varies between individuals by ±10-12 bpm, and where fat oxidation actually peaks differs by fitness and genetics — these zones are an educational estimate, not medical advice; get exercise clearance from a doctor if you have heart conditions or take heart-rate-affecting medication.
Fat-burning and cardio zones by age (simple method)
| Age | Max HR | Fat-burning 60-70% | Cardio 70-80% |
|---|---|---|---|
| 25 | 195 | 117-137 bpm | 137-156 bpm |
| 35 | 185 | 111-130 bpm | 130-148 bpm |
| 45 | 175 | 105-123 bpm | 123-140 bpm |
| 55 | 165 | 99-116 bpm | 116-132 bpm |
| 65 | 155 | 93-109 bpm | 109-124 bpm |
Computed from 220 − age with 60-70% and 70-80% bands; rounded to whole beats.
Common mistakes
- Treating the zone as the only way to lose fat — total calories out still rule; harder sessions burn more overall.
- Using 220 − age as gospel: individual max HR commonly sits 10-15 bpm off the formula.
- Choosing Karvonen but entering a resting HR taken after coffee or mid-day; measure it waking, before getting up.
- Ignoring medications — beta-blockers lower both resting and max HR, which invalidates formula-based zones.
Frequently asked questions
How is the fat-burning zone calculated?
Max HR = 220 − age, and the zone is 60-70% of it. At 35 that is 185 bpm max and a zone of about 111-130 bpm. The Karvonen option computes (max HR − resting HR) × 0.60-0.70 + resting HR, which personalizes the band using your resting pulse.
Do I burn the most fat in this zone?
You burn the highest percentage of calories from fat there, and it is where studies find maximal fat-oxidation rates for most people. But higher intensities burn more calories in total, so for pure fat loss over weeks, total work matters more than staying in the zone.
Is the fat-burning zone the same as zone 2?
Close. Zone 2 in common five-zone schemes is roughly 60-70% of max HR — a conversational pace — which is why endurance coaches prescribe lots of it: sustainable volume, low injury cost, good aerobic base.
Why does the Karvonen number differ from the simple one?
Karvonen anchors the percentage to your heart-rate reserve instead of raw max HR, so a low resting pulse raises the target. For a 50-year-old with a 60 bpm resting HR, the fat zone moves from 102-119 (simple) to 126-137 bpm (Karvonen).
Should I check with a doctor before heart-rate training?
If you have cardiovascular disease, chest pain, fainting episodes, or take beta-blockers or similar medication, yes — formulas do not apply to you, and a clinician or supervised stress test should set your ranges.