Target Heart Rate Calculator

How to use this calculator#

1. 1
   Enter your ageThat alone produces an estimated maximum heart rate and all five zones. Tanaka (208 − 0.7 × age) is the default because it fits adult data better than 220 − age, especially over 40, where the old rule reads roughly 9 bpm low at age 70.
2. 2
   Measure resting heart rate properly before entering itTake it first thing in the morning, lying still, before you get out of bed and before caffeine. Count for a full 60 seconds, or read it from a wearable's overnight low. Average three to five mornings — a single reading after a bad night can be 10 bpm off.
3. 3
   Use the Karvonen zones if you gave a resting rateKarvonen works from heart rate reserve, the gap between resting and maximum, so it accounts for how fit you are. It produces higher and more personalised targets than a flat percentage of maximum, and the difference grows the lower your resting heart rate is.
4. 4
   Spend most of your time in the low zonesEndurance training across many sports converges on roughly 80% of volume in zones 1–2 and 20% in zones 4–5. Training everything in the middle is the classic mistake — too hard to recover from, too easy to drive adaptation.
5. 5
   Cross-check the zones against how you feelZone 2 should let you hold a full conversation. Zone 4 should limit you to a few words at a time. If the numbers and the talk test disagree badly, the age-predicted maximum is probably wrong for you — the prediction carries a standard deviation of about 10–12 bpm.

The formula#

Two ways to estimate maximum heart rate#

The familiar 220 minus age rule comes from Haskell and Fox in 1971 and was never intended as a precise formula. Tanaka's 2001 equation, 208 minus 0.7 times age, fits large adult datasets better, particularly for people over 40. The gap widens with age: at 70, Tanaka gives 159 bpm against the old rule's 150.

Both carry a standard deviation of roughly 10-12 beats per minute, so an individual can sit twenty beats either side of the prediction and be entirely normal. A supervised graded exercise test is the only way to establish your true maximum.

What the five zones are for#

Zone 1 at 50-60% is warm-up and recovery. Zone 2 at 60-70% builds the aerobic base and fat oxidation, and should make up most weekly volume. Zone 3 at 70-80% improves general cardiovascular fitness. Zone 4 at 80-90% raises lactate threshold, and Zone 5 at 90-100% is reserved for short, hard intervals.

Entering a resting heart rate switches the calculation to the Karvonen method, which works from heart rate reserve: resting plus the target percentage of the gap between resting and maximum. For a 40-year-old with a maximum of 180 and a resting rate of 60, Zone 2 becomes 132-144 bpm rather than the 108-126 bpm a plain percentage gives.

Using zones sensibly#

Measure resting heart rate in the morning before getting out of bed, averaged over several days. Beta blockers, calcium channel blockers and some other medications lower both resting and maximum heart rate, which makes every age-predicted zone wrong; perceived exertion or a clinician-set target is more appropriate in that case.

These figures are general information, not medical advice. Get clearance from a doctor before starting vigorous exercise if you are over 40, sedentary, or have heart disease, high blood pressure or diabetes. Stop immediately and seek help for chest pain, unusual breathlessness, fainting or an irregular pounding heartbeat.

Worked examples#

Reference tables#

Common mistakes#

• Treating an age-predicted maximum as your actual maximumThe prediction has a standard deviation of roughly 10–12 bpm, so about a third of people sit more than 10 bpm away from it. If your zones consistently feel far too easy or impossible, trust the talk test and perceived effort over the arithmetic.
• Ignoring heart rate medicationBeta blockers, and some calcium channel blockers and antiarrhythmics, lower both resting and maximum heart rate — sometimes substantially. Every age-based zone becomes wrong on these drugs. Ask your prescriber for targets, or train by perceived exertion instead.
• Mixing the two methods without noticingA 60–70% zone means completely different bpm ranges under percentage-of-max and Karvonen — 108–126 versus 132–144 for the worked example. Following a plan written for one while your watch is set to the other means training in the wrong zone every session.
• Living in zone 3The middle zone feels productive and is the easiest place to drift into. It is too hard to accumulate large volume in and too easy to drive top-end adaptation, so weeks spent there tend to produce fatigue without progress. Keep easy days genuinely easy.

Frequently asked questions#

Key terms#

Maximum heart rate (HRmax)

The highest rate your heart can beat during all-out effort. It declines with age, is largely unaffected by training, and is only established properly by a supervised graded exercise test.

Resting heart rate (HRrest)

Beats per minute at complete rest, best measured on waking before rising. Typically 60–100 bpm in adults and often 40–60 in trained endurance athletes.

Heart rate reserve (HRR)

Maximum heart rate minus resting heart rate — the usable range between rest and all-out effort. The basis of the Karvonen method.

Karvonen method

Calculating a target as resting heart rate plus a percentage of heart rate reserve. It personalises zones to your fitness and gives higher targets than a plain percentage of maximum.

Lactate threshold

The intensity above which blood lactate accumulates faster than it can be cleared, marking the point where effort becomes unsustainable. Zone 4 work is aimed at raising it.

Cardiac drift

The gradual rise in heart rate during prolonged steady exercise at constant effort, driven by rising core temperature and falling blood volume. It is why heart rate alone can overstate intensity late in a long session.

Sources#