DecathlonFit 100M

RTOS

£60Typical price

Test score

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The Decathlon Fit 100M isn’t great with the tracking basics. A heart-rate monitor that trips up during walks and a built-in GPS that loses its bearings mean those few bright spots are not enough. Setup is simple, and the battery easily lasts 12 days, but the core tracking falls short. You can find more reliable sports tracking elsewhere for the money.

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cons

What's included?

What is it?
What can it do?
What’s the setup like?
What’s it like to wear and use?
How accurate is it?
How long is the battery life?
Should I buy it?

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KEY TEST RESULTS
Battery life
Smart notifications
Comfort

Jul 2026First reviewed by Which?
Sept 2025Released

The overall Which? test score is made up of the following star ratings, all determined by our rigorous lab tests.

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How we test smartwatches

6 Jul 2026

Ease of use

Overall
Set up
Ease of navigating menus
App
Comfort
Smart features

How we test ease of use

Includes ease of setup, charging, navigating the onscreen menus and personalising the device

Screen quality

Overall
Readability of screen in bright light
Readability of screen in low light
Scratch resistance of screen

How we test screen quality

Because you'll be using your smartwatch in a range of conditions - including outdoors in bright sunlight, at home during the day and at night-time - we rate the quality, brightness, contrast and visibility of the display. We also rate how scratch resistant it is.

Smart notifications

Overall
Phone calls
Messaging

How we test smart notifications

Rates the smartwatch’s ability to handle calls, messages (including SMS and Whatsapp messages) and notifications. The phone calls rating is based on the calls features of the watch and the sound quality of the speaker/microphone where applicable. Notifications ratings include message and social media notifications. The App rating is based on the availability of apps for receiving notifications and how useful and actionable these notifications are.

Battery life

How we test battery life

Score impacted by how long the watch lasts per charge of the battery, how quickly it charges and how much use you can get from a 15-minute charge

Health tracking

Overall
Accuracy of step tracking
Accuracy of distance tracking
Accuracy of heart rate monitor

How we test health tracking

How well the watch measures steps, distance and heart rate (for models with a built-in heart-rate monitor). Individual ratings include the accuracy of tracking for each metric (steps, distance, calories), plus the consistency of tracking between sessions. Only smartwatches with built-in GPS or a heart-rate monitor are tested for these

General
Type of smartwatch	Smartwatch
Weight (g)	43.3g
Width (mm)	42.6mm
Thickness (mm)	11.8mm
Operating system	RTOS
Removable strap	Yes

Features
Built-in heart rate monitor	Yes
Sleep tracking	Yes
NFC	No
Notifications for texts	Yes
Notifications for phone calls	Yes

Display
Screen size (mm)	50mm

Connections
iOS compatible	Yes
iOS version requirements	iOS 18 or higher
Android compatible	Yes
Android version requirements	Android 9 and higher
Built-in GPS	Yes

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DecathlonFit 100M

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pros

cons

What's included?

How we test smartwatches

Ease of use

Screen quality

Smart notifications

Battery life

Health tracking

How this product's score compares with other smartwatches we've tested

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