Karvonen formula calculator
The Karvonen formula sets a training heart rate from your resting rate and your maximum: target = resting + (maximum − resting) × intensity. Enter your numbers to see each step worked out.
Karvonen calculator
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The formula, step by step
- Maximum heart rate. Use a measured value if you have one; otherwise estimate it from age. This calculator defaults to Tanaka’s 208 − 0.7 × age[1].
- Resting heart rate. Measured after quiet rest, for example first thing in the morning.
- Heart rate reserve = maximum − resting. It is the span your heart can climb through during exercise.
- Target = resting + reserve × intensity, with intensity written as a fraction (70% = 0.7).
Worked example. A 45-year-old with a resting heart rate of 64: maximum by Tanaka = 208 − 0.7 × 45 ≈ 177. Reserve = 177 − 64 = 113. A 70% target = 64 + 113 × 0.7 ≈ 143 bpm. Seventy percent of maximum alone would be 124 bpm, which shows how much the resting rate matters.
Where the method comes from
The idea of expressing training intensity as a share of the range between resting and maximum heart rate goes back to a 1957 training study by Martti Karvonen and colleagues in Finland[2]. It is often credited, wrongly, with the 220 − age rule as well; Karvonen told the authors of a history of that equation that he never published it[3].
Exercise science calls the resting-to-maximum span the heart rate reserve, and the American College of Sports Medicine still uses it to define intensity: light is 30–39% of reserve, moderate 40–59%, vigorous 60–89%, and 90% or more is near-maximal[4]. The U.S. Physical Activity Guidelines describe relative moderate intensity in the same way, as 40–59% of reserve[5].
Why use the reserve instead of a plain percentage
A plain percentage of maximum treats every 45-year-old the same. The reserve method adds the resting rate, which differs a lot between people (the AHA notes that lower resting rates are common in athletes[6]), so two people with the same maximum but different resting rates get different targets. At low intensities the difference is largest; at 100% both methods meet at your maximum.
The trade-off is that the method inherits two uncertainties instead of one. Your estimated maximum can be off by about 10 beats per minute[1], and resting heart rate drifts with sleep, stress, caffeine and the seasons; in a study of more than 92,000 wearable users, a fifth of people had at least one week where their resting rate shifted by 10 bpm or more[7]. Use a typical resting value from several mornings rather than one reading.
Common intensity choices
- 40–59% of reserve: moderate intensity in ACSM terms[4], a sensible range for building a habit.
- 60–89%: vigorous; running, fast cycling, hard intervals.
- The 5-zone version: monitor makers’ zones (50–60%, 60–70% and so on) can be applied to the reserve as well; the zone calculator does this when you give it a resting rate.
To measure your resting rate, use the camera reader or the tap counter after sitting quietly for about 10 minutes.
Questions people ask
What is the Karvonen formula?
Target heart rate = resting heart rate + (maximum heart rate − resting heart rate) × intensity. The part in brackets is called the heart rate reserve.
Is the Karvonen method better than percentage of max?
It accounts for your resting heart rate, so it adapts to fitness. It is not automatically more accurate, because it still depends on an estimated maximum. Many coaches prefer it for that personalisation.
What intensity should I pick?
ACSM counts 40–59% of reserve as moderate and 60–89% as vigorous[4]. Easy endurance work usually sits toward the lower end, intervals toward the top.
What if I take a beta blocker?
Beta blockers can slow the heart rate[6], which shifts both resting and maximum values. An age formula will not reflect that; ask your clinician for targets.
Which maximum should I use?
A measured maximum from an exercise test beats any formula. Otherwise pick an equation and stay with it; the calculator shows how much each one changes the result.
Sources
- Tanaka H, Monahan KD, Seals DR. Age-predicted maximal heart rate revisited. J Am Coll Cardiol 2001;37(1):153–156. doi:10.1016/S0735-1097(00)01054-8. Checked 2026-10-09.
- Karvonen MJ, Kentala E, Mustala O. The effects of training on heart rate; a longitudinal study. Ann Med Exp Biol Fenn 1957;35(3):307–315. PubMed 13470504. Checked 2026-10-09.
- Robergs RA, Landwehr R. The surprising history of the “HRmax = 220 − age” equation. J Exerc Physiol Online 2002;5(2):1–10. asep.org. Checked 2026-10-09.
- Bishop DJ, et al. Physical activity and exercise intensity terminology: a joint ACSM Expert Statement and ESSA Consensus Statement. Med Sci Sports Exerc 2025;57(11):2599–2613 — Table 1, column “ACSM (2020)”, i.e. ACSM’s Guidelines for Exercise Testing and Prescription, 11th ed. doi:10.1249/mss.0000000000003795. Checked 2026-10-09.
- U.S. Department of Health and Human Services. Physical Activity Guidelines for Americans, 2nd edition, 2018 (pp. 20, 56, 60, 109). odphp.health.gov. Checked 2026-10-09.
- American Heart Association. All About Heart Rate (Pulse) (last reviewed May 13, 2024). heart.org. Checked 2026-10-09.
- Quer G, Gouda P, Galarnyk M, Topol EJ, Steinhubl SR. Inter- and intraindividual variability in daily resting heart rate and its associations with age, sex, sleep, BMI, and time of year: retrospective, longitudinal cohort study of 92,457 adults. PLoS One 2020;15(2):e0227709. doi:10.1371/journal.pone.0227709. Checked 2026-10-09.