How this calculation works
The Heart Rate Training Zones Calculator computes your Maximum Heart Rate (HRmax) and 5 distinct physiological cardio zones (Zone 1 Active Recovery through Zone 5 Neuromuscular Power) using the Tanaka and Karvonen methods.
Mathematical formula and logic
Tanaka HRmax = 208 - (0.7 × Age). Karvonen Target HR = ((HRmax - HRrest) × Intensity %) + HRrest.
Worked example
For a 35-year-old with a resting HR of 60 bpm: Estimated Max HR is 183.5 bpm. Zone 2 (Fat Burn / Base Endurance, 60-70% HRR) targets 134 to 146 BPM.
Calculation assumptions
- Tanaka formula (208 - 0.7 × Age) provides superior accuracy compared to legacy Fox (220 - Age).
- Resting heart rate measured in the morning before caffeine or physical activity.
Frequently asked questions
What is Zone 2 cardio and why is it popular?
Zone 2 (60% to 70% of Heart Rate Reserve) is conversational endurance pace where your body relies primarily on fat oxidation and lactate clearance, building mitochondrial density and cardiovascular durability without accumulating excessive fatigue.
How do I know if I am in Zone 2 during a run?
In Zone 2, you should be able to breathe through your nose and speak full sentences out loud without gasping for breath (the 'talk test').
What is Zone 4 threshold training?
Zone 4 (80% to 90% HRR) is your lactate threshold pace—the highest intensity at which your body can clear lactic acid at the same rate it is produced, sustainable for approximately 30 to 60 minutes in trained athletes.
Why is 220 - Age formula outdated?
The legacy Fox formula (220 - Age) significantly underestimates maximum heart rate in older active adults. The peer-reviewed Tanaka equation (208 - 0.7 × Age) provides a much closer clinical fit across diverse age groups.
How often should I train in Zone 2 vs Zone 5?
The popular 80/20 polarized training model recommends spending 80% of total weekly cardio volume in low-intensity Zone 2, and 20% in high-intensity Zones 4 and 5.
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