Garmin Forerunner 45S vs Garmin Forerunner 55

What Forerunner 45S does better (1) and where Forerunner 55 wins (3) — every spec side by side.

3.5Score

1 advantage≈ $200

Garmin · 2021Forerunner 55

3.6Score

3 advantages≈ $200

Higher score

2.4Display2.4

2.1Battery life3.8

3.9Build & durability3.7

Dimensions

Size comparison

Forerunner 45SForerunner 55

Drawn to the same scale from the official dimensions (front and side).

Specifications

Only differences	Garmin Forerunner 45S≈ $2003.5	Garmin Forerunner 55≈ $2003.6
Design & durability
Case size	40 mm	42 mm
Weight	32 g	37 g
Thickness	11.4 mm	11.6 mm
Height	39.5 mm	42 mm
Width	39.5 mm	42 mm
Sapphire crystal	No	No
Lens / cover glass	chemically strengthened glass	chemically strengthened glass
Strap material	silicone	silicone
Water resistance	5 ATM	5 ATM
Water rating (maker)	5 ATM	5 ATM
Display
Screen size	1.04″	1.04″
Display technology	Memory-in-pixel (transflective)	Memory-in-pixel (transflective)
Panel	Sunlight-visible, transflective memory-in-pixel	Sunlight-visible, transflective memory-in-pixel
AMOLED / OLED display	No	No
Always-on display	Yes	Yes
Resolution (width)	208 px	208 px
Resolution (height)	208 px	208 px
Pixel density	200 ppi	200 ppi
Battery
Battery life (smartwatch mode)	7 days	14 days
GPS battery life	13 h	20 h
Wireless charging	No	No
Charging	Garmin proprietary plug charger	Garmin proprietary plug charger
Health sensors
Optical heart rate	Yes	Yes
Sleep tracking	Yes	Yes
Sensors	GPS, GLONASS, Galileo, Elevate wrist heart rate monitor, Accelerometer	GPS, GLONASS, Galileo, Elevate wrist heart rate monitor, Accelerometer
Sports & navigation
Built-in GPS	Yes	Yes
Satellite systems	GLONASS, GALILEO	GLONASS, GALILEO
Sport profiles	9	15
Connectivity
ANT+ sensors	—	Yes
Smart features
Storage	—	0.03 GB
Third-party apps	Yes	Yes
Platform
Operating system	Garmin OS	Garmin OS
Platform	Proprietary	Proprietary
Works with	iOS, Android	iOS, Android