Fitbit Air vs Amazfit Helio Strap

Neither band has a screen, GPS or a mandatory fee. So the choice between them comes down to one thing: are you buying for the hours you're asleep or the hour you're in the gym?

I haven't worn either. Tests below are credited to the outlet that ran them, and I checked everything on 3 November 2026.

£84.99 on store.google.com (UK), checked 3 November 2026. £99.90 on uk.amazfit.com (UK), checked 3 November 2026.

Of these two, the Air is the lower outlay. Both have optional paid tiers you can ignore. Google's is Premium in the Google Health app, and TechRadar reports Amazfit's is a Zepp Aura subscription focused on sleep and wellness.

Fit and day-to-day wear

Google lists the Air at 12 g, With band; 5.2 g without. Amazfit lists the Helio at 20 g. On paper that's a small gap, though TechRadar's reviewer found the Helio sticks out from the wrist further than you'd guess, thicker in person than a Coros Pace 4.

Gadgets and Wearables calls the Air the easiest of the five bands it compared to forget you're wearing, and Which?'s lab gave it a top comfort rating. For overnight wear, that's the argument.

The Helio's strength is its second position. Amazfit sells an armband extension for upper-arm wear in workouts, and claims less interference when you're gripping something. I found no test measuring that for this band.

Sleep: useful, with limits

Neither band has a peer-reviewed study against polysomnography that I could find. Treat what follows as reviewers' impressions.

TechRadar's Air reviewer found total sleep time within five minutes of an Apple Watch Ultra 3, with similar stages, though its sleep score came in nine points lower. That compares two wearables to each other, and neither is a sleep lab. TechRadar's Helio reviewer wore it beside three other devices and called sleep tracking solid, while all four missed brief wakings.

That last point fits the wider research. Chinoy 2021 (peer-reviewed, 34 healthy young adults, older devices, authors report no device-company funding) found every tracker strong at detecting sleep and weak at detecting wake, with specificity from 0.18 to 0.54. My sleep accuracy explainer has more.

Neither band is a medical device, and sleep charts are estimates for general wellness. If you have symptoms or concerns, talk to a clinician.

Heart rate in training

Which? tested the Air in an independent lab (non-peer-reviewed). It reports a 0.83% error on resting heart rate and says it tracks heart rate in intense exercise better than the averages for smartwatches and fitness trackers. I read no matching lab figure for the Helio.

TechRadar's reviewer found the Air's 10 km (6.2 mi) test run had no statistically significant difference from an Apple Watch on heart rate. The reviewer's Polar H10 was malfunctioning, so there's no strap reference.

For the Helio, TechRadar's review reports readings about 10 bpm high at times on long runs against a chest strap, while calling it good enough for zones. A later TechRadar comparison, on early 2026 firmware, put peak readings typically within 2 bpm of a Garmin Venu 4.

Both results are independent and non-peer-reviewed. Firmware matters, so don't treat them as fixed. For hard sessions, a chest strap is still my pick.

Workouts and data

This is where the Helio clearly leads. Amazfit's storage claim: Offline heart rate storage up to 21 days. It also broadcasts live heart rate over Bluetooth to watches, bike computers and gym machines. It lists 50-plus sport modes, strength tracking and a Hyrox race mode.

I found no broadcast feature stated for the Air. Google says it saves 1 day of workout data, so a long weekend away from your phone is a risk. Gadgets and Wearables calls it more of a health tracker than a serious training device. Its software is the weak point for workouts, in that outlet's view.

Distance is the Air's soft spot. With no GPS, Which? measured a 10.80% daily distance error against 2.98% for GPS smartwatches. TechRadar also found distance off significantly on its 10 km run. If you run to pace, neither band replaces a watch.

Which to pick

Choose the Air for sleep and background tracking. It's the lighter, lower-priced one, with a clearer lab result.

Choose the Helio if you already wear a watch and want a second sensor for the gym, or you train for Hyrox. It costs £99.90 against £84.99 for the Air, and that small extra buys the storage and broadcast.

Want a Garmin or Polar option instead? I compare those in Whoop vs Cirqa vs Polar Loop. The sleep goal page lists the rest.