Enter your age and, if you know them, your maximum and resting heart rates. With resting heart rate, the main result uses heart-rate reserve. Without it, the main result uses a percentage of maximum heart rate and the reserve comparison waits for your input.
Why the three numbers differ
Percentage of maximum: Zone 2 uses 60–70% of maximum heart rate. If you leave maximum heart rate blank, the calculator uses the Tanaka equation, 208 − 0.7 × age, rounded to whole beats per minute. An age equation describes a population relationship and can miss an individual’s maximum substantially.
Heart-rate reserve (Karvonen): subtract resting heart rate from maximum, multiply the reserve by the desired intensity, then add resting heart rate back. This puts a person’s resting value into the calculation.
MAF starting ceiling: 180 − age is shown for comparison. Maffetone’s full method adds health and training adjustments. We do not collect that history here, so this is the unadjusted starting ceiling, not a full MAF prescription or a verified metabolic threshold.
How this matches Sarvita
Sarvita uses heart-rate reserve for its five-zone display: 50–60%, 60–70%, 70–80%, 80–90%, and 90–100%. The app assigns the shared boundary to the lower zone. With maximum 180 and resting 60, Zone 1 ends at 132, so Zone 2 is 133–144 bpm. This calculator uses the same whole-bpm boundary rule for both zone tables.
The supported app inputs are maximum 100–220 bpm, resting 40–100 bpm, and a reserve of at least 50 bpm. The calculator reports an input error outside those bounds rather than silently changing your reading. The app can derive maximum heart rate from workout history and supports custom zones; the website has no workout history and uses Tanaka when you leave it blank. An app fallback also uses 220 − age, so identical ages alone do not guarantee identical ranges. Use the same maximum and resting values for a direct comparison.
Use the talk test, then build the week
The effort should feel sustainable and allow full sentences. Heat, fatigue, caffeine and medication can change heart rate. A formula is a starting point, not an instruction to push through discomfort.
WHO’s adult activity guidance recommends 150–300 minutes of moderate aerobic activity per week, or an equivalent vigorous combination. It does not require all those minutes to sit inside this particular Zone 2 formula. Start with what is manageable and build gradually.
Read our practical Zone 2 guide, a month of Zone 2 only, Zone 2 versus HIIT and the four pillars of longevity training. You can also estimate your VO2 max.
Estimate only, not medical advice. If you have a heart condition, symptoms during exercise, or take medication that changes heart rate, ask your clinician about an appropriate intensity guide.
Saving or sharing this result keeps the full heart-rate planning range. A changed target is not a fitness measurement; use consistent measured activity or a repeat fitness test to assess progress.