Garmin heart rate zones: how to set them up properly
Your Garmin heart rate zones are only as good as the max heart rate behind them. Out of the box, the watch starts from an age-based formula; a few settings are enough to make them your own. Here is how Garmin calculates them, how to set them on the watch or in Garmin Connect, and what Running Workout does with them when your AI assistant sends a workout.
Last updated: October 25, 2026
How Garmin calculates your default zones
Garmin calculates your five heart rate zones as a percentage of your max heart rate. The watch uses the user profile you entered during setup; until it knows your real max HR, the default given in the Garmin manual is ‘220 minus your age’. With Auto Detection, which is on by default, the watch then picks up your max HR during activities and adjusts the zones.
| Zone | % of max HR | How Garmin describes it |
|---|---|---|
| 1 | 50–60% | Relaxed, easy pace, rhythmic breathing |
| 2 | 60–70% | Comfortable pace, you can still talk |
| 3 | 70–80% | Moderate pace, harder to hold a conversation |
| 4 | 80–90% | Fast and somewhat uncomfortable |
| 5 | 90–100% | Sprint, not sustainable for long |
The direct consequence: a wrong max HR shifts all five zones. With max HR set to 190, zone 2 runs from 114 to 133 beats per minute; if your real max HR is 175, your easy run will show up as zone 3 on the watch.
Try it with your own Garmin
Free to start, nothing to install: connect your Garmin, then ask Claude or ChatGPT for your first workout. It lands on your watch within a minute.
Setting your zones on the watch or in Garmin Connect
Zones are set in the watch's user profile, under heart rate zones, or from your Garmin Connect account. The Forerunner 265 manual follows this order: enter your max HR, your lactate threshold heart rate, your resting HR (the watch's measured average or a custom value), then choose what the zones are based on and adjust each one.
| Zones based on | What you need to know |
|---|---|
| BPM | You enter each zone's limits directly |
| % max HR | A reliable max HR |
| % heart rate reserve | Max HR and resting HR |
| % lactate threshold HR | Your threshold HR, measured or estimated |
Heart rate reserve is the gap between max HR and resting HR: with 190 and 50, a zone at 60–70% of reserve runs from 134 to 148 beats per minute. The manual also lets you add sport-specific zones (running, cycling, swimming), which helps because heart rate differs between sports at the same effort.
Getting a reliable max HR and threshold
The most useful max HR is the one you have actually reached, not a formula's. The Garmin manual lists three sources: Auto Detection during your activities, online calculators, and max heart rate tests offered by some gyms and health centres.
- Wear the sensor on your runs: Garmin recommends recording runs often with wrist heart rate or a chest strap.
- The lactate threshold guided test is an outdoor run with GPS on and a paired chest strap; the first estimate offers to update your zones.
- According to the manual, several runs with a chest strap are needed for accurate max HR and VO2 max values.
- A very old max HR, or one copied from another watch, is worth double-checking: every zone depends on it.
Running Workout does not give medical advice. If you have any doubt about a maximal effort, talk to a health professional before looking for your max HR.
What Running Workout does with your zones
Running Workout plan sessions are targeted by pace, as a percentage of your MAS, not by heart rate: your Garmin zones change nothing there. They do matter for the workouts you ask your AI assistant (Claude, ChatGPT or Gemini) to build with a heart rate target. It has three ways to write that target before sending it to Garmin Connect.
| Target requested | What reaches the watch |
|---|---|
| Percentage of max HR (‘easy run at 70% of max HR’) | A range in beats per minute, calculated by Running Workout from the max HR in your profile; a single value becomes ±2 points (68–72%, or 129 to 137 with a max HR of 190) |
| Beats per minute (‘between 140 and 150’) | Exactly those limits |
| Garmin zone (‘in zone 2’) | The zone number, 1 to 5, passed on as is: the watch applies your own Garmin zones |
With a zone target, your Garmin settings decide — which is why an accurate max HR on the watch matters. With a percentage, Running Workout uses the max HR from a test or the one you gave the assistant, ahead of the value declared or read from Garmin. If none is known, nothing is sent: the assistant gets an explicit error and can ask you for the value.
Frequently asked questions
Do I need to set my Garmin zones to follow a Running Workout plan?
No. Plan sessions carry their own pace targets, calculated from your MAS. Accurate zones are still useful for your free runs and for any workout you ask your assistant to build ‘in zone’.
Why did my zones change on their own?
Because Auto Detection is on by default: when the watch picks up a max HR or lactate threshold during an activity, it updates your values. You can turn it off in the watch's user profile.
Max HR percentage or heart rate reserve: which should I choose?
Max HR percentage needs only one value. Heart rate reserve takes your resting HR into account, so it needs two reliable values. Lactate threshold needs a threshold HR measured or estimated by the watch. What matters most is that the values you enter are your own.
Let your assistant write your sessions
Running Workout connects Claude, ChatGPT or Gemini to your Garmin account through the official API. Nothing to install, and no Garmin password to hand over.
See the connection guide