How Tight Should I Wear My GPS Running Watch? (Complete Guide)

I’ve bought my first running watch two years ago and when I first started using it, I didn’t know that its tightness may affect the accuracy of its readings. It was after I noticed wild swings on my data that I realized that finding the right tightness is essential in using a GPS running watch.

As a general rule, your running watch should be snug enough that the light sensors are always in contact with your skin. However, it shouldn’t be too tight that it restricts blood flow. A good rule of thumb is that you should never see the light sensors underneath the watch.

Ahead, we will discuss how tightness affects the accuracy of the watch’s readings. We will also look at the consequences of a loosely fitted watch and an overly tight watch. So if you own a running watch, fitness tracker, or a smartwatch that has a heart rate monitor, stick along cause you’re gonna need to know this.

The Right Running Watch Tightness and Positioning

The tightness of your running watch varies from activity to activity. You don’t watch it to be consistently tight all through the day because it causes discomfort, but you also don’t want to get inaccurate data by wearing it loosely.

During exercise, wear your watch 2 fingerbreadths above your wrist to prevent it from sliding up and down during the activity. It should be snug enough that the watch maintains contact with your skin at all times. You should never see the light sensor even when you’re looking at them from an angle.

During daily use, loosen your watch one hole and place it 1 fingerbreadth above your wrist bone. You don’t want to be wearing a tight watch all the time because it may cause skin irritation. A good indication is that the watch is able to move up and down your wrist.

The light sensors are still in contact with your skin and you still shouldn’t see the light sensors from an angle. However, because you’re not moving as much as when you’re in activity, wearing it a little looser is fine.

By the way, your watch has a lot of different features like sleep tracking and calorie counting. If you’re wondering if you should wear your running watch all the time, I made an article discussing exactly that. make sure to check it out after reading this article.

How The Tightness Of Your Running Watch Affect The Accuracy Of The Heart Rate Reading

Before we go into how your watch’s tightness affects the accuracy of your watch, let’s first talk about your watch’s HR monitor, the green sensor, and how it works.

Most running watches are equipped with optical heart rate technology that determines your heart rate by tracking the amount of light reflected from your veins and your tissues.

The light produced by the LEDs underneath your watch will be more scattered when the blood volume is high, therefore, a lesser amount of light is reflected back to the device. This actually means that your heart rate is high.

When blood volume is low, it means there is less light scattered and more light is reflected back to the device. This means your heart rate is low.

Based on that knowledge, we know that any interference between the light sensors and your skin can affect the data on a wrist heart rate monitor. The interference related to the tightness of the watch could be as follows:

  • More space between the light and your skin means the light can scatter in a more unpredictable manner
  • Sweat can easily get in between your skin and your watch, therefore, affecting the data (this is also the reason why wrist HR monitors don’t work very well when you’re swimming)
  • The more the watch moves or vibrates, the harder it is to get more accurate data
  • An overly tight watch could restrict blood flow and affect the watch’s readings (remember: less blood volume=more light reflected back to the watch, therefore, lower heart rate. If there is low blood volume because you constricted the blood flow, it could give a false reading that your HR is low)

Because there’s a lot of things that could affect the accuracy of a wrist heart rate monitor, wearing a chest strap that is compatible with your watch is more reliable.

If you’re really serious about using your heart rate as the basis of your training, it’s worth investing in a reliable chest heart rate monitor.

An example of this is the Garmin HRM-Dual. It’s compatible with the Garmin Forerunner and other Garmin GPS watches. It usually sells for $70 but you can sometimes get it at a discounted rate at You can check the current price at this link.

What Happens If You Wear Your Watch Loosely?

As mentioned earlier, a loose watch can affect the heart rate data because several factors can interfere with the reading of the watch such as sweat, and movement.

Aside from the heart rate, other metrics that rely on the LED light such as the SPO2 and VO2 Max could get affected as well.

If your watch relies on the accelerometer to determine distance, the excess movement of the watch when it slides up and down your wrist could also affect the accuracy of the data.

What Happens If You Wear Your Watch Very Tight?

Wearing your running watch very tight won’t give you more accurate data either. It could restrict blood flow which could decrease the blood volume on the area resulting in an inaccurate reading of your heart rate.

Aside from that, it could lead to skin irritations on your wrist. It may even affect your finger movements by compressing the nerves in the area similar to the symptoms felts by people with Carpal Tunnel Syndrome.

So, how do you get the fit just right?

How To Get Your Running Watch Fit Just Right

Here are a few things to remember that will serve as your guideline when wearing a running watch.

You Shouldn’t See The LED Light of Your Running Watch When You’re Wearing It

When wearing the watch, you should never see the light sensors underneath the body of the watch, even when you look at it from an angle.

If you see the light sensors, that means the watch is not tight enough and, therefore, it’s not reflecting the light back to the watch accurately due to the extra space in between the watch on your skin.

Your Skin Shouldn’t Be Wrinkled

If you see that (above photo) happening to your skin when you’re wearing the watch, that means the watch is too tight.

A tight watch can restrict blood flow and affect the reading of the watch. Plus, it can cause skin irritation and discomfort.

The Watch Should Not Move Up And Down When You’re Moving

During exercises, your watch should be tight enough that it doesn’t slide up and down as you move. As mentioned earlier, when the watch isn’t firmly in contact with your skin, the accuracy of the data could be affected.

But feel free to loosen it up one hole back after your exercise when you’re no longer moving as much.

Really, it all comes down to trial and error while following these guidelines. Try on different holes and positions and find out what works best for you.

Check the reading after you run and compare it to your previous runs at the same pace and route. If you feel like the readings are too far from the readings from your other runs, then there’s probably something wrong with how you’ve worn your watch.

Recommended Gear

I understand that looking for the right running gear is difficult. There are hundreds of product reviews out there recommending 10 or more products that do not seem to help narrow down your buying decision.

That is why I created a recommended product page with only 1 to 3 recommendations per running gear. That way, it’ll help narrow down your choices to only a few products that are guaranteed to give you great value for your money.

I have researched and tested these products and I’m constantly updating the page if I see something better. You can visit the page by clicking this link.

Nicho Mauricio

Running wasn't always my favorite sport. I was a CrossFit athlete and I loved every bit of it. But since the pandemic began, I was forced to stay away from the gym and train at home instead. Things got boring. That's when I decided to trail run with my friends. I instantly got hooked. So I started training and researching all things running. As a beginner, I want to buy only the best running gear and do only the best practices. This blog is where I share what I've learned in my journey and my experiences as a runner.

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