Target Heart Rate Zones (Karvonen Method)
Calculate 5 exercise heart rate zones using the Karvonen Heart Rate Reserve (HRR) method, more accurate than %MaxHR for individual training prescription.
| Zone | Range (bpm) | %HRR |
|---|---|---|
Z1 — Active recovery Walking, cool-down | 122–134 | 50–60% |
Z2 — Base aerobic Easy run/bike, long slow distance | 134–146 | 60–70% |
Z3 — Aerobic capacity Tempo / steady-state | 146–159 | 70–80% |
Z4 — Lactate threshold Threshold intervals | 159–171 | 80–90% |
Z5 — VO2max Short hard intervals, sprints | 171–184 | 90–100% |
Method: Karvonen MJ et al., Ann Med Exp Biol Fenn 1957;35:307. Max HR formula default: Tanaka H et al., J Am Coll Cardiol 2001;37:153 (208 − 0.7×age, better fit than 220−age). Zone definitions per ACSM Guidelines for Exercise Testing and Prescription, 11th ed. (2022). For precision, do a lab VO2max + lactate test.
General calculation reads
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About this tool
The Karvonen formula (Karvonen MJ et al., Ann Med Exp Biol Fenn 1957;35:307) computes target heart rate from Heart Rate Reserve (HRR), the difference between max heart rate and resting heart rate: THR = HRR × intensity + HRrest. HRR adjusts for individual fitness — a 60-bpm resting HR gives a different result than an 80-bpm resting HR even at the same %max. Estimated max HR uses the Tanaka formula (Tanaka H et al., J Am Coll Cardiol 2001;37:153): HRmax = 208 − 0.7 × age, which fits population data better than the older 220 − age formula across the full age range. The five training zones used by ACSM Guidelines for Exercise Testing and Prescription (11th ed., 2022) are: Zone 1 (50–60% HRR) very light, active recovery; Zone 2 (60–70%) light, fat oxidation, base building; Zone 3 (70–80%) moderate, aerobic capacity; Zone 4 (80–90%) hard, lactate threshold; Zone 5 (90–100%) very hard, VO2max intervals. For untrained adults beginning exercise, the AHA Scientific Statement on exercise testing (Fletcher GF et al., 2013) recommends starting at 40–60% HRR.
How to use it
- Enter your age and resting heart rate (measure first thing in the morning, lying still).
- Read your estimated max HR (Tanaka formula) and HRR.
- Use the zone table to dial in target intensity for each workout type.
- For more precise zones, do a lab VO2max + lactate threshold test.
Frequently asked questions
- Why Karvonen instead of %MaxHR?
- Karvonen accounts for resting HR — a fitter person with lower resting HR has more HR range to work with. ACSM 11th ed. (2022) recommends HRR (Karvonen) over %HRmax for prescribing exercise intensity.
- Where do I measure resting HR?
- Best: 15-30 second pulse count first thing in the morning, lying in bed before getting up. Wearables (Apple Watch, Garmin, Whoop) use overnight nadir which is essentially equivalent.
- Tanaka vs 220-age?
- Tanaka (208 − 0.7×age) fits population data significantly better than 220−age, especially for ages above 40 (where 220−age underestimates) and below 25 (where it overestimates). All major exercise-science textbooks have moved to Tanaka or similar.
- How long should I spend in each zone?
- For aerobic base, most coaches recommend the "80/20 rule" — 80% of training time in zones 1–2 and 20% in zones 4–5, minimizing zone 3. Seiler S, Int J Sports Physiol Perform 2010.
- Is data sent anywhere?
- No. All math runs in your browser.