Zone 2 Heart Rate Calculator
Determine your aerobic base training range using the Karvonen Formula.
Your Zone 2 Range
What is Zone 2 Training?
Zone 2 training is often referred to as "aerobic base training." It is the intensity level where your body primarily uses fat as a fuel source and maximizes mitochondrial efficiency. For most athletes and fitness enthusiasts, Zone 2 corresponds to a pace where you can still carry on a full conversation without gasping for air—often called "conversational pace."
How the Karvonen Formula Works
Unlike simple formulas that only use your age (like 220 – age), the Karvonen Formula is far more accurate because it incorporates your Resting Heart Rate (RHR). This accounts for your individual cardiovascular fitness level. By calculating your Heart Rate Reserve (HRR), we can find a Zone 2 range that is specific to your current physiological state.
If you are 40 years old with a resting heart rate of 60 BPM:
1. Max HR: 220 – 40 = 180 BPM
2. Heart Rate Reserve: 180 – 60 = 120 BPM
3. Zone 2 Low (60%): (120 * 0.60) + 60 = 132 BPM
4. Zone 2 High (70%): (120 * 0.70) + 60 = 144 BPM
Your Range: 132 – 144 BPM
Why Calculate Zone 2?
- Mitochondrial Health: Zone 2 stimulates the growth and efficiency of mitochondria, the power plants of your cells.
- Fat Oxidation: It trains your body to burn fat more efficiently at higher intensities.
- Recovery: It provides a cardiovascular stimulus without the massive central nervous system fatigue caused by high-intensity intervals.
- Injury Prevention: Building a strong aerobic base allows you to handle higher loads later in your training cycle.
How to Find Your Resting Heart Rate
For the most accurate results in this calculator, measure your pulse for 60 seconds immediately after waking up, while still lying in bed. Do this for three consecutive mornings and take the average. This ensures your Resting Heart Rate (RHR) is not influenced by daily stress, caffeine, or digestion.