How it works
target HR = resting + intensity% × (max − resting)
Karvonen works on your heart-rate reserve: max minus resting. Each zone takes a slice of that reserve and stacks it back on top of your resting pulse — target HR = resting + intensity% × (max − resting). Leave the max field at 0 and the calculator estimates it as 220 − age; the Tanaka formula (208 − 0.7 × age) is a slightly better population fit if you prefer to compute your own, and a measured max beats either estimate. The zone boundaries are fixed fractions of reserve: 50–60% for recovery, 60–70% for easy running, 70–80% for steady aerobic work, 80–90% for threshold sessions, and 90–100% for maximal intervals. To see why the resting anchor matters, take a runner with a max of 190 and a resting pulse of 60: at 70% intensity, Karvonen gives 60 + 0.70 × 130 = 151 bpm, while a plain percent-of-max scheme gives 133 bpm — an 18-beat gap at the same nominal effort. To turn effort into splits, pair the zones with the training pace calculator, and put an aerobic-capacity number next to your heart-rate ceiling with the VO2 max calculator.
Sources
- Karvonen heart-rate reserve method Karvonen, M. J., Kentala, E., & Mustala, O. (1957). “The effects of training on heart rate.” Annales Medicinae Experimentalis et Biologiae Fenniae 35(3), 307–315.
- Maximum heart rate estimates Fox et al. (220 − age); Tanaka, Monahan & Seals (2001), “Age-predicted maximal heart rate revisited,” J. Am. Coll. Cardiol. 37(1), 153–156 (208 − 0.7 × age).
- Heart-rate reserve method (origin) Karvonen, M. J., Kentala, E., & Mustala, O. (1957). “The effects of training on heart rate: a longitudinal study.” Annales Medicinae Experimentalis et Biologiae Fenniae 35(3), 307–315 — the original heart-rate reserve (HRR) method.
- ACSM exercise-intensity guidelines American College of Sports Medicine. ACSM’s Guidelines for Exercise Testing and Prescription, 11th ed. (2021), Wolters Kluwer — endorses %HRR (Karvonen) for prescribing aerobic exercise intensity.
FAQ
When should I recompute my heart rate zones?
Whenever an input changes. Your resting pulse drops as fitness builds, the age-based max estimate shifts every birthday, and a new field-tested max replaces the 220 − age guess entirely. Many runners refresh their zones at the start of each training block so easy days and threshold work stay honest.
What inputs matter most?
Resting heart rate is the biggest lever you control, because Karvonen anchors every zone to it — take it lying down, first thing in the morning, averaged over a few days. A measured max is the other one: the default 220 − age estimate can miss an individual by 10–20 beats, and every zone boundary moves with it.
How should I read the five zones?
Each row is a beats-per-minute window tied to a purpose: Zone 1 (50–60% of reserve) is recovery jogging, Zone 2 (60–70%) is where most easy and long-run mileage belongs, Zone 3 (70–80%) covers steady aerobic and marathon-effort running, Zone 4 (80–90%) is tempo and threshold territory, and Zone 5 (90–100%) is for short, hard intervals.
Why are these zones higher than the ones on my watch?
Most watches default to percent-of-max zones, which scale from zero rather than from your resting pulse. Karvonen scales the reserve instead, so its targets land higher: with a max of 190 and resting of 60, a 70% effort is 151 bpm by Karvonen but only 133 bpm by percent-of-max. Neither is wrong — they are different scales, so pick one and set your watch to match.
How do I find my max and resting heart rate?
For resting, check your pulse before getting out of bed on several mornings and average the readings — endurance-trained runners often sit in the 40s, while less-trained adults land in the 60s or 70s. For max, a session of hard uphill repeats or a lab test gives a real number; enter it in the max field to override the age-based estimate.
What does a typical Zone 2 range look like?
It depends entirely on your two numbers. A runner with a max of 190 and a resting pulse of 60 has a reserve of 130, which puts Zone 2 (60–70% of reserve) at roughly 138–151 bpm. Change either input and the window moves — which is exactly why personalized zones beat a generic chart.
Can beginners train with these zones?
Yes — heart-rate zones are arguably most useful for newer runners, who tend to run their easy days too hard. Start with just the age and resting-pulse fields, keep most runs inside Zone 2, and expect the ceiling to feel slow at first. That is the point.
How should my week split across the five zones?
Most training plans put the bulk of weekly mileage — commonly around 80 percent — in Zones 1–2, with the remainder as focused work in Zones 3–5. With the default example (max 190, resting 60), that means most runs held under the 151 bpm Zone 2 ceiling, and only a couple of sessions a week pushing past it on purpose.
Is this medical or coaching advice?
No. The zones come from population formulas applied to whatever you type in, and individual hearts vary widely. If you have any cardiac history, take medication that affects heart rate (beta blockers, for example), or are returning from illness, talk to a physician before structuring hard training around these numbers.
The zones on this page come from standard estimation formulas (220 − age and the Karvonen reserve method) applied to your entries — treat them as training guidance, not a medical evaluation. True max heart rate differs widely between individuals, and medication, heat, illness, and fatigue all move heart rate. Check with a physician before building intense workouts around these numbers, especially with any history of heart problems.