How it works
target HR = resting + intensity% × (max − resting)
The Karvonen formula scales each zone by your heart-rate reserve (HRR), the difference between your maximum and resting heart rate. For a given intensity you take that fraction of the reserve and add it back to your resting rate: target = resting + intensity × (max − resting). Maximum heart rate is estimated as 220 − age unless you supply a tested value; the more accurate Tanaka estimate (208 − 0.7 × age) is a common alternative. Because Karvonen anchors on your resting rate, fitter runners with a low resting pulse get lower, more realistic zone floors than a plain percent-of-max model. The five zones below use the exact %HRR boundaries this calculator applies: | Zone | Name | %HRR | Primary purpose | | --- | --- | --- | --- | | Z1 | Recovery | 50–60% | Active recovery, warm-up and cool-down | | Z2 | Easy | 60–70% | Aerobic base; most easy and long-run miles | | Z3 | Aerobic | 70–80% | Steady aerobic development, marathon effort | | Z4 | Threshold | 80–90% | Lactate threshold, tempo and cruise intervals | | Z5 | Maximal | 90–100% | VO₂max and anaerobic intervals | The same intensity number means two different heart rates depending on the method. Karvonen takes the fraction of reserve and adds resting HR; percent-of-max takes the fraction of max HR directly. For a runner with max 190 and resting 60 (reserve 130), a 70% target differs by method: | Method | 70% target HR | How it is computed | | --- | --- | --- | | Karvonen (%HRR) | 151 bpm | 60 + 0.70 × (190 − 60) | | Percent of max HR | 133 bpm | 0.70 × 190 | Karvonen generally yields a higher, more individualised target because it floors the scale at your resting pulse instead of at zero. Use it alongside the training pace calculator to cross-check effort against pace, and the VO2 max calculator to anchor your aerobic ceiling.
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
What are the 5 heart rate zones?
On heart-rate reserve they are Zone 1 Recovery (50–60%), Zone 2 Easy (60–70%), Zone 3 Aerobic (70–80%), Zone 4 Threshold (80–90%) and Zone 5 Maximal (90–100%) — the exact boundaries this calculator uses. Zones 1–2 build your aerobic base, Zone 3 is steady aerobic and marathon effort, Zone 4 works your lactate threshold, and Zone 5 develops VO₂max and anaerobic power.
What is a good zone 2 heart rate for running?
Zone 2 sits at 60–70% of your heart-rate reserve, so the exact beats depend on your own resting and max heart rate. For a runner with a max of 190 and resting of 60, Zone 2 works out to roughly 138–151 bpm. Enter your numbers above for your personal range — Zone 2 is where most easy and long-run miles should sit.
Karvonen vs max heart rate — which should I use?
Karvonen (percent of heart-rate reserve) is generally preferred because it factors in your resting heart rate, so it personalises the zones to your fitness; the ACSM endorses it for prescribing exercise intensity. Percent-of-max is simpler but ignores resting pulse and tends to set lower targets. For the same 70% intensity, a runner with max 190 and resting 60 gets 151 bpm by Karvonen versus 133 bpm by percent-of-max.
What is the Karvonen method?
A way to set heart rate zones based on your heart-rate reserve — your max heart rate minus your resting heart rate — rather than a flat percentage of max. It personalises the zones to your fitness: a runner with a low resting pulse gets lower zone boundaries than the simple percent-of-max method would give.
How do I find my maximum heart rate?
The quick estimate is 220 − age, which this calculator uses by default. It is only an average, so it can be off by 10–20 beats for any individual. A field test (such as repeated hard hill efforts) or a lab test gives a far more accurate number — enter it in the max heart rate field to override the estimate.
How do I measure my resting heart rate?
Take your pulse first thing in the morning before getting out of bed, ideally over several days, and use the average. A chest-strap monitor or fitness watch can record it automatically overnight. Typical resting rates run from the 40s for trained endurance athletes to the 60s–70s for less-trained adults.
Which zone should I run most of my miles in?
Most easy and long runs should sit in Zone 2 (easy/aerobic), roughly 60–70% of heart-rate reserve. Keeping the bulk of your training there builds aerobic fitness while leaving you fresh for the smaller amount of threshold and interval work in the higher zones.
Why are my zones different from a percent-of-max calculator?
Percent-of-max takes a fraction of your maximum heart rate directly; Karvonen takes a fraction of the reserve and adds your resting rate. Karvonen generally produces slightly higher, more individualised zones, especially for fitter runners with low resting heart rates.
Can I train by heart rate and pace together?
Yes, and many runners do. Heart rate reflects effort and responds to heat, fatigue and hills; pace reflects output. Use heart rate to keep easy days easy and pace (from a VDOT or training pace calculator) to hit specific workout targets.
Heart rate zones are estimates from population formulas and your inputs, not medical advice. Age-based max heart rate is approximate and individual variation is large. Consult a doctor before starting intense exercise, especially if you have any cardiac risk factors.