At moderate intensity your body gets a large share of its energy from fat. That “fat-burning zone” is useful for long, comfortable sessions – though total calories burned, not the fuel mix, decides fat loss.
How to use the Fat Burning Zone Calculator
- Age (years)
- Measured maximum heart rate (0 = estimate)
- Resting heart rate (bpm)
Results update as you type, every field has its own unit menu, and everything is calculated in your browser.
How it works
Enter your age or measured maximum heart rate, and your resting heart rate.
Inputs explained
| Field | What to enter |
|---|---|
| Age (years) | A number |
| Measured maximum heart rate (0 = estimate) | A number |
| Resting heart rate (bpm) | A number |
What each result means
- Heart rate reserve = [Maximum heart rate] – [Resting heart rate (bpm)]
- Zone (60–80% of max) = round(0.6×[Maximum heart rate])
- up to = round(0.8×[Maximum heart rate])
- Zoladz method from = [Maximum heart rate] – 55
- Zoladz method up to = [Maximum heart rate] – 35
- Karvonen method from = round(0.6×([Maximum heart rate] – [Resting heart rate (bpm)]) + [Resting heart rate (bpm)])
- Karvonen method up to = round(0.8×([Maximum heart rate] – [Resting heart rate (bpm)]) + [Resting heart rate (bpm)])
Example values
How the main result changes when Age changes and everything else stays at the example values above:
| Age (years) | Karvonen method from (bpm) |
|---|---|
| 17.5 | 148 |
| 26.25 | 142 |
| 35 | 137 |
| 43.75 | 132 |
| 52.5 | 127 |
| 70 | 116 |
Formula
MHR = 220 − age · Zone: 60–80% of MHR · Zoladz: MHR − 50 ± 5 to MHR − 40 ± 5 · Karvonen: (MHR − RHR) × 60–80% + RHR
Worked example
Inputs — Age (years): 35; Measured maximum heart rate (0 = estimate): 0; Resting heart rate (bpm): 65.
Results — Maximum heart rate = 185 bpm; Heart rate reserve = 120 bpm; Zone (60–80% of max) = 111 bpm; up to = 148 bpm; Zoladz method from = 130 bpm; Zoladz method up to = 150 bpm; Karvonen method from = 137 bpm; Karvonen method up to = 161 bpm.
Key terms
- Heart rate reserve
- Maximum minus resting heart rate.
Frequently asked questions
Does the fat-burning zone burn more fat?
It burns a higher share of fat, but harder exercise can burn more total calories.
Which method is best?
Karvonen, because it uses your resting heart rate.
How do I measure resting heart rate?
Count your pulse for 60 s in the morning before getting up.
Is 220 − age accurate?
It can be off by ±10–12 bpm; a measured maximum is better.