Garmin Forerunner 70 vs Fitbit Air: Which Should You Buy?

Overview

The Garmin Forerunner 70 ($249.99) is a beginner running watch with a full physiological sensor stack and Garmin's training ecosystem. The Fitbit Air ($99) is a compact health tracker built around passive monitoring and Google's data platform. These devices target overlapping buyers at very different price points, but they are not close competitors in practice.

Specs at a glance

Price: Garmin Forerunner 70 at $249.99 vs Fitbit Air at $99
Display: Forerunner 70 has AMOLED; Fitbit Air display not confirmed
GPS: Forerunner 70 has onboard GPS (chipset unspecified); Fitbit Air GPS not confirmed
Heart rate sensor: Both use wrist optical PPG (LED light measuring blood volume changes, not electrical signals)
Additional sensors: Both include SpO2 optical and skin temperature; Forerunner 70 adds HRV status tracking
Form factor: Forerunner 70 is a standard watch; Fitbit Air is a compact pebble design
Training ecosystem: Forerunner 70 integrates with Garmin Connect; Fitbit Air feeds Google's health platform
Battery life: Not confirmed for either device from available sources

GPS and tracking accuracy

The Forerunner 70 has confirmed onboard GPS, which means independent distance and pace tracking for runs without a phone. GPS chipset details are not yet published, so accuracy comparisons against other Garmin models are not possible from current data.

The Fitbit Air's GPS situation is unconfirmed. What is confirmed is heart rate accuracy during exercise. In a road bike sprint test, the Fitbit Air produced limits of agreement of plus or minus 6 bpm against a reference device. The Amazfit Cheetah 2 Ultra returned plus or minus 3 bpm in the same test. For steady-state cardio the gap may be tolerable, but for interval work or sprint efforts, 6 bpm error is enough to misread training zones.

The Forerunner 70 uses the same PPG hardware approach as the Forerunner 265 and 965. No independent accuracy figures are available yet, but Garmin's optical sensors at this tier have historically performed better than plus or minus 6 bpm in controlled tests.

Battery life

Neither device has published confirmed battery figures at time of writing. This is a meaningful gap in the available data. For a buying decision based on multi-day tracking or long-run battery endurance, both devices require checking manufacturer specs directly before purchase.

For athletes: who wins?

Running: Forerunner 70. Onboard GPS, Garmin's training load metrics, and a full physiological stack make it the only real option for runners who want structured training data.
Trail and outdoor: Forerunner 70. Confirmed GPS and Garmin's ecosystem cover this. Fitbit Air has no confirmed GPS and is not positioned for trail use.
Triathlon: Neither device is confirmed to support multisport modes. The Forerunner 70 is the more plausible option given its running focus, but this requires verification before purchase.
Recovery and passive health monitoring: Both devices track HRV, SpO2, and skin temperature. The Forerunner 70 ties these into Garmin's Body Battery and HRV Status features. The Fitbit Air feeds Google's platform, which raises legitimate data privacy considerations for users who want to keep biometric data off a large ad-supported ecosystem.

Verdict

For anyone doing structured exercise, the Forerunner 70 is the clear choice. It has GPS, a real training ecosystem, and sensor accuracy that is not yet proven to be as limited as the Fitbit Air's confirmed 6 bpm exercise heart rate error. The Fitbit Air is cheaper and may suit someone who wants passive health data and nothing more, but the exercise tracking accuracy issues and data privacy trade-offs are real weaknesses at any price.

Buy the Forerunner 70 if you run, train by heart rate zones, or want Garmin's coaching tools. Buy the Fitbit Air only if $99 is a hard ceiling and you have no expectations of accurate workout tracking.