Understanding your heart-rate zones
The five-zone model divides heart-rate reserve into bands that correspond to distinct training purposes. The ACSM classifies 40–59% HRR as moderate and 60–89% HRR as vigorous intensity.
| Zone | % of heart-rate reserve | Typical purpose |
|---|---|---|
| Zone 1 | 50 – 60% | Very light — warm-up, cool-down, recovery sessions |
| Zone 2 | 60 – 70% | Light — long-duration aerobic base and fat-oxidation training |
| Zone 3 | 70 – 80% | Moderate — sustained aerobic conditioning |
| Zone 4 | 80 – 90% | Hard — lactate-threshold and tempo intervals |
| Zone 5 | 90 – 100% | Maximal — short intervals near maximal capacity |
- The maximum heart rate used here is the age-based estimate 220 − age, which carries an individual error of roughly ±10 beats per minute or more; a measured maximum makes the zones more accurate.
- Beta-blockers and some other medications lower heart-rate response, making heart-rate zones unreliable; perceived exertion is often used instead in that situation.
- Zone percentages are conventions, not physiological absolutes — thresholds between easy and hard efforts vary between individuals and are best located with testing.
- Health agencies advise people with cardiovascular symptoms, risk factors or long inactivity to seek medical guidance before beginning vigorous (zone 4–5) training.
What is a target heart rate zone?
A target heart rate zone is a range of heartbeats per minute that corresponds to a chosen exercise intensity. Training in defined zones lets people control effort objectively: lower zones support long, easy endurance work, while higher zones develop speed and maximal capacity.
This calculator uses the Karvonen method, published by Martti Karvonen and colleagues in 1957. Instead of taking simple percentages of maximum heart rate, it takes percentages of heart-rate reserve (HRR) — the difference between maximum and resting heart rate — and adds the resting rate back. Because resting heart rate falls as aerobic fitness improves, Karvonen zones adapt to the individual rather than depending on age alone.
The percentage bands used here (50–60, 60–70, 70–80, 80–90 and 90–100% of HRR) follow the five-zone convention widely used in endurance training. For context, the American College of Sports Medicine classifies 40–59% of HRR as moderate intensity and 60–89% as vigorous intensity in its exercise-prescription guidelines.
Heart-rate zones are educational guidance for healthy exercisers, not a medical prescription. Medications such as beta-blockers change heart-rate response, and anyone with cardiovascular symptoms or risk factors should discuss appropriate exercise intensity with a healthcare professional.
How to use this target heart rate calculator
- Enter your age in years — the calculator estimates maximum heart rate as 220 − age.
- Enter your resting heart rate, ideally measured in the morning before getting out of bed, by counting your pulse for 60 seconds or using a heart-rate monitor.
- Read the five zones; each shows the beats-per-minute range corresponding to that percentage of your heart-rate reserve.
- Match the zone to your session goal — long easy sessions in zones 1–2, sustained aerobic work in zone 3, harder interval work in zones 4–5 as fitness and experience allow.
The formula behind the Karvonen method
The Karvonen method first computes heart-rate reserve (HRR) as estimated maximum heart rate minus resting heart rate, then places each zone boundary at a percentage of that reserve above the resting rate.
Example: a 40-year-old with a resting heart rate of 60 bpm has an estimated maximum of 180 bpm and an HRR of 120 bpm. The 70% point is 0.70 × 120 + 60 = 144 bpm.
Common mistakes
- Entering a daytime or post-coffee pulse as the resting heart rate — it should be measured at rest, ideally on waking, or the zones shift upward.
- Confusing percentage of heart-rate reserve (Karvonen) with percentage of maximum heart rate; the same percentage gives different beats-per-minute values in the two systems.
- Doing all training in the middle zones — conventional endurance practice places most volume in zones 1–2 with selected harder sessions, rather than constant moderate-hard effort.
- Ignoring that the 220 − age estimate can be 10 or more beats off for an individual, which shifts every zone boundary.
- Chasing zone 5 numbers while on heart-rate-lowering medication such as beta-blockers, when heart-rate targets no longer reflect true intensity.
Frequently asked questions
What is the Karvonen formula?
The Karvonen formula, published by Karvonen, Kentala and Mustala in 1957, sets a target heart rate as a percentage of heart-rate reserve added to the resting rate: Target HR = (HRmax − resting HR) × %intensity + resting HR. It personalizes training zones because it accounts for the individual's resting heart rate.
What heart rate should I exercise at?
It depends on the session's purpose. Under the ACSM intensity classification, moderate exercise corresponds to 40–59% of heart-rate reserve and vigorous exercise to 60–89%. Long easy endurance work is usually done around 50–70% of reserve (zones 1–2), while interval training uses 80% and above. People with health conditions should confirm appropriate intensities with a clinician.
How do I measure my resting heart rate?
Count your pulse at the wrist or neck for 60 seconds shortly after waking, before getting up, caffeine or stress, or read the overnight value from a heart-rate monitor or watch. Typical adult resting rates are about 60–100 beats per minute, and endurance-trained people are often below that range.
Why do my zones differ from percent-of-max zones?
The Karvonen method takes percentages of the reserve between resting and maximum heart rate, then adds the resting rate back, so each zone boundary sits higher in beats per minute than the same percentage of maximum alone. For example, 70% for a person with HRmax 180 and resting HR 60 is 144 bpm by Karvonen but 126 bpm as a simple percentage of maximum.
Is Zone 2 training really at 60–70% of heart-rate reserve?
Zone definitions vary between coaching systems — some use percentage of maximum heart rate, some use heart-rate reserve, and some use lactate or ventilatory thresholds. In the five-zone heart-rate-reserve convention used by this calculator, zone 2 spans 60–70% of reserve. What matters is using one system consistently.
How accurate are these zones?
The zones inherit the uncertainty of the 220 − age maximum estimate, which commonly misses an individual's true maximum by 10 or more beats per minute. Measuring maximum heart rate in a supervised test, or anchoring zones to lactate or ventilatory thresholds, produces more precise personal zones.
References
- Karvonen MJ, Kentala E, Mustala O. The effects of training on heart rate: a longitudinal study. Annales Medicinae Experimentalis et Biologiae Fenniae 1957; 35(3): 307–315.
- American College of Sports Medicine. ACSM's Guidelines for Exercise Testing and Prescription. Wolters Kluwer — exercise intensity classification by %HRR.
- Tanaka H, Monahan KD, Seals DR. Age-predicted maximal heart rate revisited. Journal of the American College of Cardiology 2001; 37(1): 153–156.
- American Heart Association. Target heart rates chart. heart.org.
- Centers for Disease Control and Prevention (CDC). Measuring physical activity intensity — target heart rate and estimated maximum heart rate. cdc.gov.