Garmin Forerunner 645 vs 735XT – Simple Product Comparison

Garmin Forerunner 645 vs 735XT – Simple Product Comparison

In this product battle, we compare the Garmin Forerunner 645 vs the Garmin Forerunner 735XT.

They are both high quality GPS watches packed with plenty of impressive features. But there are some significant differences between the two. This goal of this article is to make those differences crystal clear.

Features Limited to Garmin Forerunner 645

Built-in Music Storage & Music Apps - Forerunner 645 Only:

The Forerunner 645 was the first Garmin to introduce music storage. It has around 3.5GB of storage to play with, which works out to about 500 songs.

And yes, the Forerunner 645 is also compatible with two of the most popular music apps in the world, namely:

  • Spotify – Works with Forerunner 645M
  • Deezer – Works with Forerunner 645M

Contactless Payments - Forerunner 645 Only:

This is another nifty feature that can only be found in the Forerunner 645.

Basically, it allows you to make payments with your watch, and it’s a surprisingly convenient feature to have. Personally I wouldn’t let this feature sway my decision, but it’s a pretty cool addition if you end up going for the FR645.

Barometric Altimeter - FR645 Only:

If you take your running seriously, you want to have an altimeter built into your watch. This piece of tech uses changes in atmospheric pressure to measure your incline and decline data.

When combined with the FR645’s GPS technology, you get a more accurate measurement of distance, incline and decline data. This is particularly important if you do hill training regularly or you enjoy trail running.

Galileo Satellite - FR645 Only:

Galileo satellite tracking is Europe’s answer to GPS (American technology) and GLONASS (Russian technology).

Some people suggest Galileo satellite tracking is more accurate than both, but that is debatable and a separate discussion altogether. The point is, the Forerunner 645 has Galileo tracking built-in. The FR735XT does not. 

WiFi Connectivity - FR645 Only:

On the surface, this doesn’t seem like a big deal, but over time, the convenience of WiFi connectivity adds up. Basically, it means you can use WiFi rather than Bluetooth to connect to your phone or your computer (once the watch is connected).

If you’ve tried using Bluetooth more than 3 times in your life, you will quickly appreciate how much better WiFi is for communicating information between technological devices.

Can Display Running Power - Forerunner 645 Only:

Admittedly you need to have one of the following three accessories in order for the FR645 to display running power.

You also need to download the Garmin Running Power App and sync it with your watch. The point is that the FR645 gives you this option.

Personally, if I wanted running power, I would combine the FR645 and the HRM-Run, mainly because it gives you the added benefit of improved heart rate data (the same is true of the HRM-Tri, but it’s slightly more expensive, and I’m not a triathlete).

Features Limited to the Forerunner 735XT:

Open Water Swimming - FR735XT Only:

This is one of two major advantages that the FR735XT has over the FR645. The benefit is self-explanatory. The 735XT can track your distance and pace in open water environments like the ocean or a big dam. This is crucial for triathletes. 

Side note – It’s worth mentioning that the FR645 and the FR735 can both track pool swimming.

Triathlon Mode - FR735XT Only:

This is by far the biggest advantage that the 735 has over the 645

The Forerunner 735XT is a multisport triathlon watch. That means it can track all three disciplines of a triathlon (run, swim and cycle), and you only need to push a single button to transition from one discipline to the next.

If you’re into triathlons, this is a non-negotiable requirement.

Key Similarities - Forerunner 645 vs 735XT


Wrist HRM

Indoor + Outdoor Running

Indoor + Outdoor Cycling

Pool (Indoor) Swimming

Multiple Cardio Modes


24/7 Activity Tracking

Sleep Tracking


ANT+ Connectivity

Bluetooth Connectivity

V02 Max Estimator

Advanced Running Dynamics

Key Differences - Forerunner 645 vs 735XT

Built-in Music

Contactless Payments

Barometric Altimeter

Galileo Satellite

WiFi Connectivity

Garmin Running Power

Open Water Swimming

Triathlon Mode

Visual Summary of Key Features

Forerunner 735XT Features

Forerunner 645 Features

Which one would I buy, if I had to choose today?

If you’re a runner or you spend a lot of time at the gym –  go for the Forerunner 645. It’s a much better watch for people who focus primarily on running, and you can still track cycling,  pool swimming and a bunch of different cardio modes at the gym.

The addition of music functionality and payments from the watch mean the Forerunner 645 has similar technology to that found in the Garmin Fenix 5 Plus, which is basically double the price. 

If you’re a triathlete – Go for the Forerunner 735XT. Open water swimming and triathlon mode are absolutely essential for triathletes. 

On the flipside, if you aren’t a triathlete, the Forerunner 645 is definitely the better option.

Best for runners and fitness enthusiasts

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