How the maths work
Maximum heart rate is the highest number of beats per minute your heart can produce during all-out effort. The popular “220 − age” rule overestimates MHR for older adults; the Tanaka et al. (2001) formula MHR = 208 − 0.7 × age fits population data better and is now standard in exercise physiology textbooks.
Heart rate reserve (HRR) is MHR minus your resting heart rate. The Karvonen formula calculates a target by taking a percentage of HRR and adding back your resting rate: THR = ((MHR − RHR) × intensity) + RHR.
What each zone is good for
- Warm-up / very light (50–60% HRR) — mobility, recovery, warm-up before harder work.
- Moderate / Zone 2 (60–70% HRR) — aerobic base building. The pace endurance athletes spend the most time in.
- Vigorous / cardio (70–85% HRR) — lactate threshold work, tempo runs, hard intervals.
- Peak (85–100% HRR) — sprints, race finishes, VO₂max intervals. Used briefly, not sustained.
How to measure your resting heart rate
Take your pulse first thing in the morning, before getting out of bed, for one minute. Repeat across three to five mornings and use the average. A modern fitness watch or ring will track it automatically and is usually within 1–2 bpm of a manual count.
Limits
Tanaka MHR is a population average; individual MHRs can vary by 10–20 bpm. Beta blockers and similar cardiovascular medications suppress heart rate and make these zones inapplicable. If you have a cardiac condition, consult your cardiologist for personal target zones.