There are many simple formulas for establishing your theoretical maximum exercise heart rate. However when I exercise I routinely find myself in a maximum exertion Zone if these numbers are to be believed. As I am nowhere near maximum exertion I believe the formula must not be correct. I can run a 10K in an hour. I can exercise strenuously for an hour in a military-style fitness program. I would like to set my fitness watch correctly. What are good guides or formula to use for maximum heart rate?

Multi-marathoner here, now encroaching on my 67th year on this earth.

For years, I used the standard

MHR = 220 - age

There are some studies that have refined this formula

MHR = 208 - 0.7(age)
MHR = 207 - 0.7(age)

Using these with my current age (66), I get 154, 161.8 and 160.8, respectively. Not much difference between the three, if you ask me.

Also, I've used the 80% of MHR as a gauge for distance running, so for me, that would be 123.2, 129.44 and 128.64.

Given that my resting heart rate is in the 56 - 63 range, the 80% target suggests I'm working well.

IHTH.

The subject of heart rate zones is a little bit controversial, especially if you are trying to be precise. But, that being said, most people do need some starting guidelines.
Here is a calculator based on "threshold heart rate". Your "threshold" is the max heart rate you can hold for 20 minutes continuous, and you arrive at it by testing yourself. Go for a run and keep pushing yourself until you think you can possibly hold it for 20 minutes and then back off just a tiny bit. As you get closer to the 20th minute, constantly, repeatedly push up against what you think the limit is and back off a smidge if necessary. Your threshold is the average heart rate over the last couple minutes. If you have enough energy to sprint at the end, you did it wrong. You need to be right at where you can just barely complete the run and are begging yourself to stop.

After you have your Threshold Heart Rate, you can plug it into the calculator. The formulas are also on the web.

https://www.endurancepath.com/...ing-zone-calculator/

Personally, my max heart rate is quite a bit above the simple formulas, but throughout most of my life it has been below the formulas. My MHR has remained fairly constant and even gone up a bit, while the formulas all predict a downward trend with age.

The numbers you refer to are merely rough guidelines. Getting the numbers you are asking for requires monitoring and recording heart rates through the cardio zones. Also, as your heart progresses from exercise, it will become more efficient. When I was cycling/racing back in the 80's, my resting heart rate was around 30 bpm, normal non-exercise rate was in the 50s and my maximum was 201. This as a 45 year old man.

Training in the various cardio zones accomplishes different tasks in one's training. You need to determine what your goals are specifically and then target the appropriate zone. These zones are usually determined as a percentage of your maximum rate although there are other methods using percentages based on the difference between resting and maximum. I kept it simple ans used the first method.

Google "cardio zones" and you'll get more a lot more information.

If you really want to determine your max heart rate, you should go to a cardiologist that does those stress tests and tell him what you want.

I read that from some book about heart and exercise and how to get the most from aerobic, anaerobic, and fat burning zones.

I had to get one done after I got a bad reaction from an allergy shot and the allergist wouldn't allow me to continue until I had one. I think he was covering his ass.

The only way to properly do it is with a VO2 Max test.

You can get "close," assuming "average" health, by a combination of the age calculation and carefully noting "perceived effort" (PE). In this case the aspect of PE in which you're interested is that heart rate just before the point at which you can no longer hold a conversation without effort. That will be "approximately" your anaerobic threshold. If you can establish resting heart rate (lowest heart rate while sleeping) there are calculations from that you can use to refine the ballpark numbers.

You have to be careful in attempting to establish Maximum Heart Rate (MHR). If you have any cardiovascular issues at all, you could well kill yourself in the process of doing that. I run myself up to my MHR all the time, by the simple expedient of working out until my heart rate will go no higher. But I happen to know my CV system will tolerate that.