Zone 2 Heart Rate Calculator
Calculate your target aerobic training zone using the Karvonen method for better accuracy.
Your Zone 2 Range:
What is Zone 2 Heart Rate Training?
Zone 2 training is the "aerobic base" intensity where your body primarily uses fat as its main fuel source. Physiologically, it is defined as the intensity where lactate levels stay below 2.0 mmol/L. For most athletes, this feels like an effort level of 3 or 4 out of 10.
Training in this zone improves mitochondrial density and efficiency, allowing you to run, cycle, or swim faster at lower heart rates over time. It is the foundation of most endurance programs, often making up 80% of total training volume.
How to Calculate Your Zone 2 Range
While many use a simple percentage of Maximum Heart Rate (60-70%), the Karvonen Formula is widely considered more accurate because it accounts for your individual fitness level via your Resting Heart Rate (RHR).
The Math Behind the Calculator
- Max HR: 220 – Age
- Heart Rate Reserve (HRR): Max HR – Resting HR
- Zone 2 Low (60%): (HRR × 0.60) + Resting HR
- Zone 2 High (70%): (HRR × 0.70) + Resting HR
Example Calculation
If you are 40 years old with a resting heart rate of 60 bpm:
- Max HR: 180 bpm
- HRR: 120 bpm (180 – 60)
- 60% Intensity: (120 × 0.6) + 60 = 132 bpm
- 70% Intensity: (120 × 0.7) + 60 = 144 bpm
- Zone 2 Range: 132 – 144 bpm
The "Talk Test" Verification
Technology isn't perfect. To verify you are truly in Zone 2, use the "Talk Test." You should be able to hold a full conversation comfortably without gasping for air. If you can only speak in short sentences, you have likely drifted into Zone 3.
| Metric | Zone 2 (Aerobic) | Zone 3 (Tempo) |
|---|---|---|
| Effort (RPE) | 3-4 / 10 | 5-6 / 10 |
| Primary Fuel | Fat Oxidation | Glucose / Glycogen |
| Breathing | Rhythmic & Easy | Steady but noticeable |