💚 Zone 2 Heart Rate Calculator
Calculate your personalized Zone 2 heart rate for optimal aerobic training, fat burning, and longevity. Science-backed methods from leading researchers.
| Zone | HR Range | % Effort | Duration | Primary Benefit | When to Use |
|---|---|---|---|---|---|
| Zone 1 Recovery |
50-60% | Very Easy | Unlimited | Active recovery, warm-up | Rest days, cool-down |
| Zone 2 Aerobic Base |
60-70% | Easy | 45-90 min | Mitochondrial health, fat burning, longevity | Most training sessions (80% of volume) |
| Zone 3 Tempo |
70-80% | Moderate | 30-60 min | Tempo endurance | Minimize – “grey zone” |
| Zone 4 Threshold |
80-90% | Hard | 10-30 min | VO2max, lactate threshold | 1-2x/week intervals |
| Zone 5 Maximum |
90-100% | Max | 1-10 min | Peak power, anaerobic | Race pace, sprints |
20% of training: Zone 4-5 (high intensity) – Develops VO2max, performance
Minimal Zone 3: “The grey zone” – too hard for aerobic development, too easy for high-intensity adaptations
Myth: The “fat burning zone” (low intensity) burns the most fat.
Reality: Zone 2 burns the highest percentage of calories from fat (~60-70%), but higher zones burn more total calories.
Why Zone 2 Matters: Sustainable for 45-90 minutes, improves metabolic flexibility, builds mitochondrial density, and enhances long-term fat oxidation capacity. It’s the foundation for metabolic health and longevity.
What is Zone 2 Training?
Research by Dr. Iñigo San Millán demonstrates that Zone 2 training is the most effective intensity for mitochondrial function and long-term metabolic health. For comprehensive training planning, use our Workout Intensity Calculator.
📐 Karvonen Formula (Most Accurate Method)
HRR = Max HR – Resting HR
Zone 2 Lower = Resting HR + (HRR × 0.60)
Zone 2 Upper = Resting HR + (HRR × 0.70)
📝 Example Calculation
Step 1: Max HR = 208 – (0.7 × 35) = 208 – 24.5 = 183 BPM
Step 2: HRR = 183 – 60 = 123 BPM
Step 3: Zone 2 Lower = 60 + (123 × 0.60) = 60 + 73.8 = 134 BPM
Step 4: Zone 2 Upper = 60 + (123 × 0.70) = 60 + 86.1 = 146 BPM
Zone 2 Range: 134-146 BPM
Heart Rate Calculation Methods Compared
The Science of Zone 2 Training
Mitochondrial Health and Function
Zone 2 training is the most effective intensity for improving mitochondrial function. At this intensity, mitochondria work at maximum efficiency, consuming lactate and pyruvate as fuel. Research shows that Zone 2 corresponds to the lactate threshold 1 (LT1), where blood lactate remains stable at approximately 2 mmol/L.
This steady-state intensity stimulates mitochondrial biogenesis—the creation of new mitochondria—without overwhelming cellular systems. The result is improved cellular energy production, enhanced insulin sensitivity, and better overall metabolic health.
Fat Oxidation and Metabolic Flexibility
During Zone 2 training, your body derives 60-70% of energy from fat oxidation. This intensity teaches your body to efficiently use fat as fuel, improving metabolic flexibility—the ability to switch between burning carbohydrates and fats.
Studies demonstrate that trained individuals can oxidize fat at rates 1.5-2 times higher than untrained individuals during Zone 2 exercise. This adaptation supports weight management, improves insulin sensitivity, and reduces metabolic disease risk.
Zone 2 Training Volume Recommendations
Zone 2 adaptations require sufficient duration. While sessions under 30 minutes provide some benefit, 45-90 minute sessions are optimal for maximizing mitochondrial adaptations and fat oxidation improvements.
The Polarized Training Model
Research by Dr. Stephen Seiler on elite endurance athletes reveals a consistent training pattern: approximately 80% of training volume at low intensity (Zone 1-2) and 20% at high intensity (Zone 4-5), with minimal time in Zone 3.
80/20 Training Distribution:
- 80% Zone 1-2: Builds aerobic base, sustainable long-term, low injury risk
- 20% Zone 4-5: Develops VO2max, improves lactate threshold
- Minimize Zone 3: “Grey zone” – too hard for aerobic development, too easy for high-intensity adaptations
Best Activities for Zone 2 Training
🚴 Cycling
Low-impact, easy to control intensity, sustainable for long durations. Indoor cycling allows precise HR control.
🚶 Incline Walking
Excellent for beginners or those recovering from injury. Very low impact while reaching Zone 2 HR.
🏃 Easy Running
True Zone 2 requires running slower than expected. This builds the aerobic engine for faster race paces.
🏊 Swimming
Full-body, low-impact training. Heart rates run 10-15 BPM lower in water, so adjust zones accordingly.
🚣 Rowing
Engages upper and lower body while maintaining steady Zone 2 intensity with minimal joint stress.
⛸️ Cross-Country Skiing
Full-body aerobic training used by elite endurance athletes for Zone 2 base building.
Zone 2 Training FAQs
How often should I do Zone 2 training?
Aim for 3-5 Zone 2 sessions per week, totaling 2-6 hours depending on your goals. For general health and longevity, 2-3 hours weekly is sufficient. Competitive athletes may train 6-8+ hours in Zone 2.
Can I do Zone 2 training fasted?
Yes. Fasted Zone 2 training can enhance fat oxidation adaptations. However, it’s not necessary—fed-state training works equally well for building aerobic capacity. Choose based on personal preference and schedule.
How long until I see results?
Initial improvements in power/pace at Zone 2 HR appear within 4-6 weeks. Significant mitochondrial adaptations occur over 8-12 weeks. Long-term metabolic benefits continue developing for 6+ months.
Is Zone 2 better than HIIT?
They serve different purposes. Zone 2 builds aerobic base and mitochondrial density. HIIT improves VO2max and lactate threshold. The optimal approach combines both: 80% Zone 2, 20% high-intensity (polarized training).
Why does my Zone 2 pace feel so slow?
True Zone 2 often feels “too easy” for motivated athletes. This is normal and correct. The adaptations happen at the cellular level (mitochondria), not through muscle fatigue. Trust the process and resist the urge to speed up.
⚠️ Important Medical Disclaimer
This calculator provides general guidance based on established exercise science formulas. Individual responses vary significantly. Always consult with a qualified healthcare provider or exercise physiologist before starting a new training program, especially if you have pre-existing cardiovascular conditions, take medications affecting heart rate (beta-blockers, etc.), or have been sedentary. If you experience chest pain, severe shortness of breath, dizziness, or unusual symptoms during exercise, stop immediately and seek medical attention.
