Garmin Forerunner 45 vs Garmin Forerunner 55: Running Watch

Garmin Forerunner 45 vs Garmin Forerunner 55

In the Forerunner series, the Forerunner 45 is a successful entry-level, small and full-featured running watch. Dating from 2019, this model is now replaced by the complete Forerunner 55, with new functions including PacePro and daily training suggestions, an improved display, and almost doubled battery life. What are the differences between the 2 watches and which model to choose? Should you sell your Forerunner 45 for the Forerunner 55? Comparison and opinion.

Garmin releases new models every year in its Forerunner series, watches specially designed for running. The Forerunner 45 and the Forerunner 55, its successor, are the entry-level models. At the same time, small, light, and at an affordable price, these watches offer complete functions, in any case, sufficient for most beginners to occasional runners.

The new Forerunner 55 is offered at the same price as the Forerunner 45 when it is released. However, the old model benefits from a reduction of $35 and is, therefore, a good buying opportunity for people who do not need the new features of the recent model.

Both watches are small and ultralight (less than 40g). The Forerunner 45 was offered in 2 case sizes (39 and 42 mm), the small model being particularly well suited to people with thin wrists. Unfortunately, this is no longer the case with the Forerunner 55, which only offers a single-size case (42 mm). Pity. In return, the bracelet is interchangeable without tools, and the screen can display up to 4 data fields instead of 3.

Pros and Cons

Forerunner 45Forerunner 55
Ease of useCompact size and comfort
Suitable for all wristsFull sports functions
Physiological measures
(stress, effort, recovery)
Daily training suggestions
No third-party app supportNo interchangeable bands
Straps feel a bit cheapThe display could be improved

Key Features

Forerunner 45Forerunner 55
Garmin Forerunner 45Garmin Forerunner 55
ModelForerunner 45Forerunner 55
Release dateApril 30, 2019June 2, 2021
CompatibilityAndroid + iOSAndroid + iOS
ColorsBlue, Black, White, RedAqua, Black, White

Forerunner 45

Garmin Forerunner 45

Garmin Forerunner 45 Rear

Released in 2019, the Forerunner 45 is an entry-level watch replacing the Forerunner 35. It is compact, light, inexpensive, and has been designed for occasional athletes who are looking for the essentials of running functions. It is more than sufficient for many athletes who run for fun.

It has a color screen, optical cardio on the wrist, GPS, connected functions, activity monitoring with sleep, and stress level analysis.

It measures VO2max (physical condition), offers a vocal coach the ability to load workouts and interval training. It offers an incident detection and incident assistance function.

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AIt is available in 2 case sizes (45 and 45S versions), it adapts to all wrists, including thin wrists (from 129 mm in circumference). So here is a watch that knows how to be discreet!

Forerunner 55

Garmin Forerunner 55

Garmin Forerunner 55 Rear

Replacing the Forerunner 45, the Forerunner 55, released in 2021, is more complete, has a new optical sensor, and offers better autonomy. On the other hand, it is only available in single case size, 42 mm, and Forerunner 45 (the large model).

It takes the characteristics of the Forerunner 45. Still, it is enriched with many previously only offered functions on the higher models in the range, such as PacePro or the Daily Training Suggestions, to progress without anything. Know. It also benefits from new sports profiles. The functions for swimming, non-existent on the old model, are now present.

Technical Specifications

Forerunner 45Forerunner 55
Screen typeColor display, anti-glareColor display, anti-glare MIP
Screen Resolution208 x 208 pixel208×208 pixels
ConnectivityiPhone, Android, PC, Mac. 
Bluetooth wireless data transfer
iPhone, Android, PC. 
Bluetooth Smart wireless data transfer
Heart rate monitoring
Calorie burn
Interval training
Pace alarm
Heart rate monitoring
Calorie burn
Interval training
Pace alarm
Time/distance alarm
Automatic activity goal
Training effect
Automatic sleep log
Battery13 h in GPS mode, 7 days in watch mode20 h in GPS mode, 14 days in watch mode
Water resistance5 ATM (50 meters)5 ATM (50 meters)
WeightSmall: 32 g / Large: 36 g37 g
Dimensions42 x 42 mm x 11.4 mm42 x 42 x 11.6 mm

Forerunner 45

Garmin now offers a round rather than rectangular screen, chemically reinforced glass for greater strength, and, like its Fenix ​​5 and Fenix ​​5 Plus, different case and strap sizes to fit all wrists. 

The Forerunner 45 is therefore available in 2 models:

The Forerunner 45S is a small model designed for thin wrists (124 to 185 mm in circumference). Its case is only 39.5 mm in diameter for a thickness of 11.7 mm. With 32 g on the scale, it is one of the featherweights. It is available in 2 colors: white and iris.

The Forerunner 45: this is the standard model. It is suitable for wrists with a circumference of 129-197 mm. Its case is 42 mm in diameter, 11.4 mm thick, and weighing only 36 g. It is available in 2 colors: black and red.

Garmin offers a new color anti-glare screen (transflective MIP technology) of 208 x 208 px and 26.3 mm in diameter (compared to the square monochrome screen of 128 x 128 px previous model, the Forerunner 35).

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You can change the watch face on this new model either by creating your own dial from personal photos or by downloading one from among the thousands available on the Garmin website.

This model offers a battery life of 7 days in watch mode and 13 hours in GPS mode, i.e., roughly the same autonomy as the old model but with more intensive use of the watch (measurement of stress throughout the day and compatibility with 3 satellite systems). This is sufficient for occasional sports use, including several short trips during the week or a long trip.

Forerunner 55

The watch offers a design similar to that of the Forerunner 45, with a compact case, chemically reinforced glass, and a 20mm wide silicone strap that can be changed without tools. It has 5 buttons. To assist the user, Garmin has printed a short description in English around the screen. The watch is available in 4 colors: black, white, Monterra gray, and sea green.

Unlike the previous model, which was available in 2 case sizes (39.5 and 42mm), this one is only offered in one size (42mm). Too bad for people with thin wrists, especially for a watch intended for use 24 hours a day. The watch remains small even on a thin wrist but is still less discreet than the Forerunner 45S.

The Forerunner 55 screen is in color, non-touch, and retains the same definition as the previous model (108 x 108 pixels). This is a bit tight compared to the 240 x 240 pixels of the Forerunner 245, whose case is only 1 mm more in diameter. MIP anti-glare technology provides a very readable 64-color display even in direct sunlight (the light received is reinjected into the screen to serve as a backlight)

Several dials (watch face) preloaded in memory with the possibility of personalizing them, including the addition of photos. Garmin offers more downloadable watch faces on its Garmin Connect) IQ platform. Nothing new here.

Among the new features, it is now possible to download widgets, data fields, and apps via Garmin Connect IQ, as the other watches in the series already do. We can thus add the “breathing frequency” widget, which is not installed by default. Widgets also provide a complete display with summary data.

The watch now displays up to 4 data fields (down from 3) and up to 4 customizable data screens. In addition, the interface is improved with revisited and more complete displays.

Garmin makes this model much more autonomous than the previous one. (In our detailed review of the old model, we underlined the somewhat low battery life.) We reached 20 hours in GPS mode and 14 days in a connected watch, roughly double! This is excellent for an entry-level watch!

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Activity Monitoring

Forerunner 45Forerunner 55
Interval trainingYesYes
Advanced workoutsYesYes
Daily workout suggestionsNoYes
Race time predictorYesYes
Recovery timeNoNo
Heart rate alarmsYesYes
Calories by heart rateYesYes
Blood oxygenation (SpO2)NoYes
Aerobic Training Effect
Recovery timeNoYes
CyclingRecord various metricsRecord various metrics
OutdoorRecord various metricsRecord various metrics

Garmin Forerunner 45 Sleep

Garmin Forerunner 45 Steps
Forerunner 45

Garmin Forerunner 55 Sleep

Garmin Forerunner 55 Steps
Forerunner 55

Smart Features

Forerunner 45Forerunner 55
Smartphone notificationsYes (calls, texts, and apps)Yes (calls, texts, and apps)
Wireless paymentsYesNo
Music storage and playbackYesYes
Phone music controlYesYes
MeteorologyYes (temperature, forecast), with SmartphoneWeather forecast
Other smart featuresFind my phone
Find my phone

Apart from a more recent Garmin Elevate ™ optical heart rate monitor on the Forerunner 55 (it works underwater), the 2 watches have the same sensors: GPS chip compatible with GPS, GLONASS, and GALILEO, heart rate monitor on the wrist, accelerometer. In addition, they are compatible with some external ANT + and Bluetooth Smart sensors but not with power sensors (cycling, running).

It is best to use a heart rate chest strap for precise heart rate measurements and associated physiological measurements (VO2max, recovery, calories burned, etc.). These watches are compatible with the Garmin HRM Dual belt, which offers the dual ANT + and Bluetooth Smart protocol. Please note, this belt cannot be used for swimming.

The advantage of the new Forerunner 55 is that it offers optical cardio that works underwater.

These models do not offer GPS navigation. They record the route taken to display it on a map after the exit but do not display a GPS track on the watch. They indicate the speed, pace and distance covered thanks to the GPS (outdoor) or the accelerometer (indoor training on carpet or track).

The 2 watches receive Smartphone notifications (incoming call notifications, reading SMS and social network messages), allow access to the Google calendar, the weather forecast, or even download watch faces.

On Forerunner 55, you can also download widgets, apps, and data fields. You can also access new information (hunting/fishing calendar, for example)

The Forerunner 55 benefits from new features for more comprehensive health monitoring, such as hydration monitoring and female health monitoring (menstrual cycle, pregnancy).


Garmin offers 2 reliable and quality easy-to-use watches, offering a user-friendly and intuitive interface and complete tools for running, all at a low price. These entry-level models will not disappoint their users.

As its name suggests, the Forerunner series is designed primarily for running and for the higher models in the range, trail, and triathlon. If running is not your main activity, turn to another model instead.

These 2 models are already very complete and will satisfy many runners of all levels, beginners to occasional runners, even regular runners, running for fun. Most of the functions for running are there. Next, we will turn to the higher models in the range (see our comparison of Garmin Forerunner watches ).

The Forerunner 55 is significantly more complete than the old model. It has newer optical cardio that works underwater, advanced functions for swimming (the other is not intended for swimming), new profiles, and sports functions allowing complete running training. Except for running dynamics and GPS navigation, we have almost a Forerunner 245 (the model just above) with, in addition, a revised graphical interface. Autonomy, much better, is also a great asset. For 35 USD more to pay only, there is no hesitation. This is the model we recommend.

However, the Forerunner 45 offers one advantage to consider: available in 2 sizes; offers more flexibility for people with small wrists. With the small model (Forerunner 45S), we gain almost 3 mm in case diameter without losing screen quality (the size of the screen is the same as the large model). The watch also benefits from a price reduction, which is appreciable if you have a limited budget. Be careful, however, if you want to swim: this model does not have a swimming profile and does not offer any means of measuring heart rate in the water.

Finally, if you already have a Forerunner 45, the model change is not really necessary unless you practice swimming in addition to running or if you absolutely want to benefit from the new functions and the improved battery life.