What Are My Heart Rate Zones?

The formula everyone uses was never really researched

220 − age stuck because it's easy to do in your head, not because it's good. It was a convenient line drawn through limited data decades ago.

The better one is Tanaka: 208 − 0.7 × age, from a 2001 meta-analysis of 351 studies covering 18,712 people aged 20 to 86. It carries roughly half the error.

They cross at exactly 40

This is the part worth knowing, because it means the old formula isn't uniformly wrong — it's wrong in opposite directions either side of one age.

Set them equal: 220 − a = 208 − 0.7a → 12 = 0.3a → a = 40.

Age	220 − age	Tanaka	Old formula is
20	200	194	6 too high
30	190	187	3 too high
40	180	180	identical
50	170	173	3 too low
70	150	159	9 too low

So the traditional formula pushes young athletes to train harder than they should, and tells older ones their ceiling is lower than it is. Older athletes are the ones it short-changes most, and that's the group most likely to be handed it by a gym poster.

Why it asks for your resting heart rate

Because the zones use the Karvonen method, which works from your heart rate reserve — maximum minus resting — rather than a flat percentage of maximum.

Zone = resting + (percentage × reserve)

This matters more than it sounds. Two people with the same maximum and resting rates of 45 and 70 are not doing the same work at 150 bpm. A percentage-of-maximum model can't tell them apart; Karvonen can.

For a 35-year-old with a resting rate of 60:

• Max: 208 − (0.7 × 35) = 183.5
• Reserve: 183.5 − 60 = 123.5
• Easy (60–70%): 134 to 146 bpm
• Hard (80–90%): 159 to 171 bpm

Measure your resting rate properly

Every zone is built on it, so an error here propagates into all of them.

On waking. Lying still. Before you get up, check your phone, or think about the day. Count for a full minute, or use a wearable's overnight figure. Do it several mornings and take the lowest sensible value.

A reading taken sitting at a desk is commonly ten to twenty beats higher — which pushes every zone up with it.

The number most people get wrong

The easy range. Nearly everybody trains above it, and always in the same direction.

Most recreational endurance training is meant to be genuinely conversational, with only a small share of hard work. Left to feel, people drift upward until every session sits in an unproductive middle — too hard to recover from properly, too easy to drive real adaptation.

Seeing "easy" as an actual number is usually a surprise. Holding it usually feels far too slow at first. That's the point.

The conversation test beats the watch: if you can't speak in full sentences, you're above the easy range whatever the strap says.

How much to trust any of this

Not as much as the precision suggests. Age-predicted maxima carry a standard deviation of 10–15 bpm — wider than a single zone.

Your true maximum could genuinely be 15 beats either side of the figure here. So these are a starting range to calibrate against feel, not thresholds to obey. If you want a real number rather than a population average, that takes a proper field test or a lab test.

Two things that shift the picture

Sport. Maximum heart rate is typically several beats lower cycling than running, and lower again swimming — body position and how much muscle is involved. Train seriously in more than one and you want a separate maximum for each.

Everything else. Heat, altitude, caffeine, illness, poor sleep and stress all move heart rate at a given effort. Heart rate also drifts upward through a long session at constant effort, and lags behind effort at the start of one.

Print the heart rate training card and log whether your easy sessions were actually easy. That column is usually the interesting one.

Not medical advice. These are estimates from population formulas with a margin of error wider than a zone. Beta blockers in particular lower both resting and maximum heart rate substantially, making age-predicted zones meaningless. If you have a heart condition, take medication affecting heart rate, or are new to hard exercise, speak to a doctor first.

Sources: Tanaka et al. via SimpliFaster · Fox vs Tanaka in marathon runners (PMC)