Training Heart Rate: Find Your Zones

Max heart rate: the formulas (220 minus age and Tanaka)

Training by heart rate starts with one ceiling: your maximum heart rate (MHR), the highest number of beats per minute your heart reaches at full effort. Almost everything else — zones, pace, intensity — is calculated as a percentage of that figure. The catch is that measuring true MHR requires a supervised stress test, so in everyday life we lean on formulas.

The best-known is the Fox and Haskell formula from the 1970s:

It is easy to remember, but it carries a wide standard deviation: roughly ±10 to 12 bpm. In other words, your real MHR could easily sit 10 beats above or below what the formula says. That is why a more modern equation gained ground — the Tanaka formula (2001), validated in a large study across a broad age range:

Here is how the two diverge with age. Oddly enough, they cross at exactly 40:

For younger people, "220 − age" overestimates; past 50, it underestimates. Tanaka corrects both ends. There are also population-specific variants, such as Gulati for women (206 − 0.88 × age). To compare the numbers without doing the arithmetic by hand, the Heart Rate Calculator shows the estimate from the different formulas at once.

The five training zones

With MHR in hand, effort is split into bands. The most common model has five zones, each with a different physiological goal. Taking someone with an MHR of 190 bpm as an example (a 30-year-old by the classic formula), the bands as a plain percentage of MHR look like this:

A well-built program does not live in a single zone. The polarized model, popular with runners and cyclists, suggests spending most of your time (around 80%) in zones 1 and 2 and reserving short slices for zones 4 and 5. Zone 3 — the infamous "gray zone" — is where many people train all the time: too hard to recover from, too easy to drive real adaptation.

Fat-burning zone vs aerobic zone

The "fat-burning zone" (usually 60–70% of MHR, zone 2) earned a reputation as the weight-loss zone, and there is a misunderstanding worth clearing up. It is true that at low intensity a larger proportion of the calories you spend comes from fat. But proportion is not total.

In 30 minutes at an easy pace you might burn 250 kcal, with 60% from fat — 150 kcal of fat. In the same 30 minutes at a hard pace you burn 400 kcal, with 40% from fat — 160 kcal of fat, plus the afterburn of keeping calorie expenditure elevated post-workout. So the percentage drops, but the total fat burned can actually rise, and overall energy expenditure is much higher.

The Karvonen method (heart rate reserve)

Calculating a zone as a flat percentage of MHR has a flaw: it ignores your fitness. Two people of the same age share the same estimated MHR, but the fitter one has a more efficient heart that beats slower at rest. The Karvonen method fixes this using heart rate reserve (HRR), the gap between the ceiling and the floor:

Resting heart rate is measured lying down, right after waking, before you get out of bed — count the beats for 60 seconds. In adults it usually sits between 60 and 80 bpm; in well-conditioned people, below 60.

Here is a worked example. A 30-year-old, MHR 190, resting HR 60:

• HRR = 190 − 60 = 130 bpm
• Target at 70%: (130 × 0.70) + 60 = 91 + 60 = 151 bpm
• Target at 80%: (130 × 0.80) + 60 = 104 + 60 = 164 bpm

Notice the difference from the simple math: 70% straight off MHR would give 133 bpm, but Karvonen points to 151 bpm for the same 70% intensity. The reserve formula produces higher, more individualized targets because it anchors the band to your actual resting rate. The Heart Rate Zones Calculator (Karvonen) applies exactly this method: enter your age and resting HR and it returns all five zones already adjusted.

Putting it to work in real training

Knowing the numbers is half the job; using them is the other half. A few practical ways to put the zones to work:

• Base runs: stay in zone 2 (light). If you can hold a full-sentence conversation while running, you are at the right pace — that is the "talk test".
• Interval training (HIIT): alternate bursts in zone 4–5 with recovery in zone 1–2. For example: 1 minute hard, 2 minutes easy, repeated.
• Active recovery: the day after a hard session, stay in zone 1 to move blood without adding fatigue.

One important caveat: heart rate has inertia. It takes a minute or two to rise and fall, climbs with heat, dehydration and caffeine, and drops with accumulated fatigue (overtraining). Anyone on beta-blockers or other heart medication will have an artificially lowered MHR — the formulas do not apply in that case. Always pair the monitor with your perceived effort: if the number says zone 3 but your body screams zone 5, trust your body.

Frequently asked questions

"220 − age" or Tanaka: which formula should I use?

For most people, Tanaka (208 − 0.7 × age) is more accurate, especially below 25 and above 50. "220 − age" is still handy for its simplicity, but keep the ±10 bpm error in mind. Neither replaces a real stress test, which is the gold standard when precision matters.

What is the difference between the plain-percentage method and Karvonen?

The plain-percentage method calculates the zone straight off MHR (e.g. 70% of 190 = 133 bpm). Karvonen uses heart rate reserve (MHR minus resting HR) and adds the resting rate back in, producing higher, more personalized targets. For the same 70% intensity, the guide's example gives 133 bpm with the simple math and 151 bpm with Karvonen.

Is training above my estimated MHR dangerous?

Going a few beats past your calculated ceiling usually just means your real MHR is higher than the formula predicted — common, given the ±10 bpm spread. It is not, by itself, a danger sign. The real warning is symptoms: dizziness, chest pain, an irregular beat or shortness of breath out of proportion to the effort mean stop and seek a medical check.

Do I need a chest strap, or is a wrist watch enough?

Chest straps (which read the heart's electrical signal) are more accurate, especially during short intervals and sudden pace changes. Optical wrist sensors have improved a lot and work well for steady base training, but they lag and drift more at high intensity and with heavy arm movement.

My resting HR has dropped over time. Is that a good sign?

Generally, yes. A fitter heart pumps more blood per beat, so it needs fewer beats for the same work — which is why athletes have a low resting HR. A gradual drop over weeks of training is a great marker of progress. Sudden drops, or ones paired with symptoms, do deserve a check-up.