Apple Watch heart rate zones calculator

What should your Apple Watch heart rate zones be?

This calculator writes Diastra's bands as the five zones on your Apple Watch. The bands are called Easy, Threshold and VO₂max. The space between Easy and Threshold is the gray band. Easy is the Zone 2 most runners know.

Every zone starts from your max heart rate. The calculator estimates your max with the Tanaka formula, which is 208 minus 0.7 times your age^[3]. A max you type replaces that estimate. Each edge is your max times its percentage, rounded up to a whole beat. So the first beat in each zone is the first whole beat that reaches that zone's percentage.

Take a 40-year-old man who has never measured his max. The formula gives him 180. His zones come out like this.

• Zone 1 · under 108
• Zone 2 · 108 to 142
• Zone 3 · 143 to 156
• Zone 4 · 157 to 165
• Zone 5 · 166 and up

A 40-year-old woman gets the same Zones 1, 4 and 5. Her Zone 2 runs from 108 to 149, and her Zone 3 runs from 150 to 156.

The zones are not the same width. The man's Zone 2 is 35 beats wide, and his Zone 4 is 9 beats wide. Each edge comes from blood lactate research or from the lines coaches use. Those points are spaced unevenly, so the zones are uneven too.

Where does each zone edge come from?

Zone 2 ends near the first lactate threshold

The first lactate threshold is called LT1. It is the point where lactate in your blood first starts to rise above its resting level. A 2025 panel of 14 sport scientists and coaches agreed that Zone 2 training is best done right below that point^[5].

Blood tests on 165 recreational runners put LT1 at 78.9% of max for men and 83.6% for women on average^[4]. The calculator ends Zone 2 one beat under 79% for men and one beat under 83% for women. All 165 runners together averaged 80.7%. So Zone 2 ends one beat under 80% when you leave sex blank.

Zone 2 starts at 60% of max

A scale built from the training of world-class distance runners starts its lowest zone at 60% of max^[6]. The paper lists that zone for warm-ups, cool-downs and easy long runs. Its next zone runs from 73 to 82% of max and covers long runs, uphill runs and progressive runs. The paper treats both zones as low intensity. Diastra's Easy band takes in the first zone and most of the second, so the calculator's Zone 2 starts at 60%.

Zone 3 is the gray band

Zone 3 runs from the top of Easy to one beat under 87% of max. Diastra calls this range the gray band. The same world-class scale has a moderate zone at 83 to 87% of max^[6]. The paper lists it for threshold runs, fartlek and half marathon and marathon race pace. Runners at the top of the sport plan real sessions in this range.

Zone 4 is Threshold

Threshold is named for LT2, the second lactate threshold. Above LT2, lactate in your blood climbs steeply. The 165 runners reached LT2 at 90.6% of max on average^[4]. The women averaged 91.7% and the men 89.9%. Zone 4 runs from 87% to one beat under 92%, so all three averages fall inside it.

Zone 5 is VO₂max

Zone 5 starts at 92% of max and runs up to your max. VO₂max is the most oxygen your body can use when you go all-out. The name tells you what the band trains. It does not mean every minute in Zone 5 is spent at your VO₂max.

Coaches draw nearly the same lines

A 2025 survey asked endurance athletes and coaches who use five zones where each zone starts^[7]. Runners in the survey started Zone 3 at 79.6% of max on average. They started Zone 4 at 86.6% and Zone 5 at 92.3%. The calculator starts a man's Zone 3 at 79%, Zone 4 at 87% and Zone 5 at 92%.

The survey's runners started Zone 2 at 69.8% of max. The calculator starts Zone 2 at 60%, where Easy starts.

Why is this different from Apple's automatic zones?

Apple's guide says the watch sets its zones from your health data as percentages of your max heart rate^[1]. Apple's 2022 announcement said the zones can be made by hand or calculated from personalized Health data^[2]. Neither page names the max the watch starts from or the percentage where each zone starts. This page describes Apple's guide as it read on October 7, 2026, for watchOS 27.

This calculator prints both numbers. The card shows the max it used and says whether that max came from your age or from a number you typed. The table under the first heading lists the percentage behind every edge.

An age formula can land far from your real max. All-out tests on 3,320 healthy adults gave an age formula that missed real max heart rate by a typical 10.8 beats a minute^[9]. A max you saw at the end of a hard race or test brings every zone closer to you.

A real max can also come in under the formula. Say an all-out test puts the 40-year-old woman's max at 172. That is 8 beats under the formula's 180. Her Zone 2 becomes 104 to 142, and her Zone 3 becomes 143 to 149. Zone 4 becomes 150 to 158, and Zone 5 starts at 159. Every limit she types moves down by 4 to 7 beats. The guide to finding your max on Apple Watch covers the all-out efforts runners use.

Apple's guide does not say whether its zones change with sex. This calculator ends Zone 2 higher for women. Women in the lactate study reached LT1 at a higher share of max than men did^[4]. A lab study of 100 adults found the same pattern^[8].

How do you type your zones into the watch?

Apple lets you set the lower and upper limits of Zones 2, 3 and 4 by hand^[1]. The calculator prints those six numbers under Type these into your watch. Open the Apple Watch app on your iPhone and tap My Watch. Then go to Workout, then Heart Rate Zones, and tap Manual^[1]. The Settings app on the watch has the same menu under Workout.

The 40-year-old man above types 108 to 142 for Zone 2, 143 to 156 for Zone 3 and 157 to 165 for Zone 4. Heart rate zones on Apple Watch has the steps on the watch itself, the zone view during a run and heart rate alerts.

Apple's guide gives no limits to type for Zones 1 and 5. It also does not say where the watch puts them after a manual change. The calculator still shows both. Zone 1 is anything under your Easy band, and Zone 5 is your VO₂max band.

How close will these zones be to your own thresholds?

Each edge is a group average. Your own threshold can land somewhere else, and some edges land closer than others.

The lactate study checked the edges runner by runner^[4]. It took the average LT1 share for each runner's sex and applied it to the max that runner reached on the treadmill. The real LT1 fell within about 16 beats of that estimate for 95 of every 100 runners. The same check came much closer for LT2, the threshold Zone 4 is drawn around. Both estimates missed by more when the max came from the Tanaka formula.

So the top of Zone 2 is the edge most likely to miss your own line. Let your breathing check it. Easy running is a pace you can hold a conversation at. Slow down when talking in full sentences gets hard. Do that even when the watch still shows Zone 2. The guide on why Zone 2 running feels so slow explains why heat, hills and long runs push heart rate up.

How does Diastra use these zones?

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, and it tells you which one it used. Easy, Threshold and VO₂max come from that max with the same edges as this calculator, and Easy's top edge is split by sex. Your watch taps your wrist when you drift out of your band on a run. Diastra credits only the minutes that held and shows over the weeks whether your training is working. Getting fitter. Holding steady. Slipping. How Diastra draws your bands lists every edge and the study behind it.