How do heart rate zones work on Apple Watch?

How does Apple Watch set your heart rate zones?

Apple Watch shows your effort in five heart rate zones, from easier to harder. Apple's guide says each zone is a percentage of your maximum heart rate. The watch works the zones out from your health data and personalizes them^[1]. This page describes Apple's guide as it read on October 4, 2026, for watchOS 27.

The watch needs your date of birth first. Apple says the zones are calculated only if your date of birth is in the Health app on your iPhone^[1].

You see the zones in cardio workouts like an outdoor run. Turn the Digital Crown during the workout to reach the Heart Rate Zone view. It shows your zone, your heart rate, your time in that zone and your average heart rate.

Open the Fitness app on your iPhone after the run to look back. Tap Sessions, tap the workout, then tap Show More next to Heart Rate. A graph shows Apple's estimate of how long you spent in each zone^[1].

What is Apple's default based on?

Apple describes the inputs in general terms. The guide says the zones come from your health data and need your date of birth. It does not print the formula for your max heart rate or the percentage where each zone starts.

Your date of birth gives your age. Age is the usual starting point for a max heart rate when nobody has measured it. A common research formula is 208 minus 0.7 times your age^[3]. Apple does not say which formula it uses, so read that one as an example. That formula gives 180 for a 40-year-old.

An age formula gives the middle of a crowd. Max heart rate differs a lot from one person to the next. Measured max heart rate in a study of 165 recreational runners averaged 188 beats a minute, give or take about 8^[4]. The first lactate threshold is where lactate starts to rise in your blood, and it marks the top of easy running. A fixed percentage of each runner's measured max missed that threshold by about 7 beats a minute on average. The miss grew to about 9 beats when the max came from the age formula^[4].

Apple's guide also says the zones are personalized from your health data. So the watch may use more than your age. The guide doesn't list what else goes in.

Why might the default zones not fit you?

Two things set any zone line. One is the max heart rate the line starts from. The other is the percentage where the line is drawn.

Start with the max. A 40-year-old gets 180 from the age formula. Say a hard race finish shows that runner a max of 190. Every line drawn from 190 moves up. The line at 79% of max moves from 142 to 150 beats a minute.

Then the percentage. Blood tests on 165 recreational runners put the first lactate threshold at 78.9% of max for men and 83.6% for women on average^[4]. Many zone charts end Zone 2 at 70% of max. Apple doesn't list its percentages. Compare the zone your watch shows during a run with your own numbers below.

A measured max brings the line closer to your own threshold. It still can't put the line right on it. The averages hide a wide spread. Forty-three of every 100 runners in that study were already past their first threshold at 80% of max^[4]. A lab study of 100 adults found the first threshold anywhere from 60 to 90% of max^[5]. Any zone line is a starting estimate.

Heart rate also moves within one run. Fifteen young trained runners in one study held one fairly hard speed for 40 minutes. Their heart rate climbed by about 4% of max on average while the speed stayed the same^[6]. So the zone on your wrist can change while your pace holds still.

Which bands should you type into the watch?

The bands on this page come from your max heart rate and carry Diastra's names.

• Easy is the Zone 2 you know, drawn more accurately. It runs from 60% of max to 79% for men and 83% for women. Its top edge is near where blood tests on runners find lactate starting to rise.
• Threshold runs from 87 to 92% of max. It is the fastest pace you can hold before fatigue stacks up quickly.
• VO₂max runs from 92% of max up. VO₂max is your aerobic capacity. That is the most oxygen your body can use when you go all-out.

The space between Easy and Threshold is the gray band. Easy ends at 80% of max for anyone who doesn't set a sex.

Here is where each band goes on the watch. Apple's guide lists only Zones 2, 3 and 4 for editing^[1].

Your own numbers are below. The Easy, Gray and Threshold rows are the limits you will type into the watch.

How do you change your heart rate zones on Apple Watch?

Apple lets you set the lower and upper limits of Zones 2, 3 and 4^[1]. Its guide does not say how the watch sets Zones 1 and 5 once you type the other three.

Follow these steps on your Apple Watch.

1. Open the Settings app.
2. Go to Workout, then Heart Rate Zones.
3. Tap Manual.
4. Tap Zone 2 and enter its lower and upper limits.
5. Do the same for Zone 3 and Zone 4.

You can make the same change on your iPhone. Open the Apple Watch app, tap My Watch, then go to Workout > Heart Rate Zones and tap Manual.

Type these numbers from your bands.

• Zone 2 · your Easy row
• Zone 3 · your Gray row
• Zone 4 · your Threshold row

Say a man has a measured max of 185. His Easy band runs from 111 to 146. His gray band runs from 147 to 160. His Threshold band runs from 161 to 170. He types these limits.

• Zone 2 · 111 to 146
• Zone 3 · 147 to 160
• Zone 4 · 161 to 170

His VO₂max band starts at 171 and runs up to his max of 185.

How do you stay in your Easy band during a run?

The Heart Rate Zone view shows where you are during the run. You can also add alerts to a workout in Apple's Workout app. Apple's own example is an outdoor run with an alert for a heart rate of 133 to 141 beats a minute^[2].

1. Open the Workout app on your Apple Watch.
2. Turn the Digital Crown to the workout you want.
3. Tap the Alerts button.
4. Tap the alert you want and set it up.

Set the heart rate range to your Easy band for an easy run. Apple says the alerts you add are used whenever you do that workout^[2].

Expect your heart rate to climb on hot days. Ten trained men in one study cycled at one steady, moderate effort in a hot room and again in a cool room. The hot room was 95°F, and the cool room was about 72°F. Their heart rate rose 11% between minute 15 and minute 45 in the hot room. It rose only 2% in the cool room^[7]. Slow down or walk until you are back in Easy.

Effort helps on days when heart rate runs high. People of every fitness level rated the first breathing threshold at about 12.5 on the 6 to 20 effort scale in 863 lab tests^[8]. That threshold is the point where your breathing first picks up. A 12.5 falls between light and somewhat hard, and an easy run stays below it. Why Zone 2 running feels so slow covers heat, hills and drift in more depth.

When should you update your zones?

Update them when your max changes. Regular training does not raise your max. The large review behind the age formula found the same age line for active and inactive people^[3]. A higher number shows up when a hard race or an all-out test finally reaches it.

The age formula drops 0.7 beats a year^[3]. Check limits that come from the age formula once a year. Check them again after any race that shows a new max. Finding your max on Apple Watch shows where to look in your workouts. The max heart rate formulas page compares the age formulas.

How does Diastra use your Apple Watch heart rate?

Diastra reads every workout your Apple Watch saved in Apple Health. It finds your max heart rate in those workouts, in a guided test or in a number you type. Then it tells you which one it used.

Diastra draws Easy, Threshold and VO₂max from that max and sets the top of Easy by sex. A tap on your wrist tells you when you drift out of your band. Diastra credits only the minutes that held. It shows over the weeks whether your training is working. Getting fitter. Holding steady. Slipping. How Diastra draws your bands explains where each edge comes from.