Strap a Google Fitbit Air to one wrist and an Apple Watch Ultra 3 to the other, run 10 kilometers, and the screenless $99.99 band tracks heart rate within 3 beats per minute and calories within 25 of Apple’s $799 flagship. The gap only blows open when satellite positioning enters the picture, and that is the whole story of who should buy which.
Those numbers come from a side-by-side field test run by TechRadar’s fitness and wearables team, which sent both devices on the same UK evening run during a heatwave. For Apple, the result cuts two ways. The cheaper rival nearly matched it on the readings most people check, then fell apart on the one metric runners actually obsess over.
The 10km Test on Two Wrists
The setup was simple. One reviewer, one 10-kilometer evening run, a Google Fitbit Air on the left wrist and an Apple Watch Ultra 3 multisport smartwatch on the right. A Polar H10 chest strap was meant to serve as the accuracy referee, since electrical heart rate monitors read the heart’s electrical signal directly rather than estimating it from blood flow. The strap malfunctioned mid-test, so there is no chest-strap data to publish.
That leaves the two wrist devices to be judged against each other, with one useful piece of history attached. In earlier testing, the Apple Watch Ultra 3 matched an electrical heart rate monitor exactly, so it stands in here as the trusted reference. Both wearables read your pulse the same way, through optical sensors that shine light into the skin and watch how blood flow changes.
Here is how the run logged on each device.
| Metric (same 10km run) | Google Fitbit Air | Apple Watch Ultra 3 |
|---|---|---|
| Average heart rate | Within 3 bpm of Apple | Reference (matched chest strap in prior tests) |
| Calories burned | About 25 kcal higher | Reference reading |
| Distance logged | 10.43 km | 10.03 km |
| Average pace | Roughly 10 sec per km faster | Reference pace |
| In-workout steps | 9,342 | Not recorded |
| Stride length, vertical oscillation | Not recorded | Recorded |
| Onboard GPS | No (uses phone) | Yes (dual-frequency) |
Heart Rate and Calories Land Within Touching Distance
The headline finding is how little daylight there is between the two on the body’s core signals. Average heart rate came in just 3 beats per minute apart across the full run. For a casual user checking whether a workout pushed them into a higher effort zone, that is a rounding error.
Calories told the same story. The Fitbit Air’s estimate ran less than 25 calories above the Apple Watch Ultra 3’s count for the whole session. Calorie figures on any wearable are educated guesses, blending heart rate with movement and personal data, so no two devices will ever agree to the decimal. A 25-calorie spread on a 10-kilometer run is close enough to trust day to day.
What makes this notable is the sensor pedigree on the more expensive wrist. Apple’s optical heart rate reader has been one of the most reliable wrist-based options on the market, beaten only by dedicated chest and arm straps. The Fitbit Air clinging that tightly to it, off a sensor packed into a pebble the size of a thumbnail, is the kind of result that quietly resets expectations for a budget tracker.
It also fits a wider pattern in affordable wearables getting the basics right. Heart-rate and stress accuracy used to be the dividing line between cheap and premium bands, the same gap that earlier brought richer health metrics to mid-range devices through software, such as the Garmin stress detection rollout for smartwatches. The optical-sensor floor keeps rising.
The 400-Meter Problem: No Onboard GPS
Then the run hit the metric where price still buys something real. The Fitbit Air carries no onboard GPS (Global Positioning System, the satellite network that pinpoints location), so it borrows the signal from a paired iPhone instead. The Apple Watch Ultra 3 has its own L1 and L5 dual-frequency receiver built in.
The damage showed up in two places. The Fitbit Air logged the run at 10.43 kilometers against Apple’s 10.03, a gap of roughly 400 meters on a route that drew an identical map with the same finishing point on both devices. It then claimed a pace 10 seconds per kilometer faster than Apple recorded, on a hot day with steep climbs and descents at either end that made for a slower-than-usual effort.
Different Sensors, Different Stories
Neither device sees the run the same way, and the differences go beyond accuracy. The Apple Watch Ultra 3 surfaces the granular running technique data a coach would want, while the Fitbit Air leans on simple, all-day movement counting. What each captured on the same outing breaks down clearly.
- Apple only: stride length and vertical oscillation, the measure of how much you bounce with each step, plus ground contact time and cadence.
- Fitbit only: total steps taken during the workout, logged at 9,342, a figure the Apple Watch does not record inside a run.
- Both, closely matched: average and real-time heart rate, calorie burn, and the route map itself.
- Both, but diverging: distance and pace, where the Fitbit’s borrowed positioning drifts.
The split says a lot about who each device is built for. Apple is feeding a runner who wants to refine form over months. The Fitbit Air is feeding someone who wants a steady, low-fuss read on activity across the whole day, which is also why its screenless pebble runs up to a week on a charge while the Ultra 3 measures battery life in hours.
A $700 Price Gap Reframes the Result
Put the spec sheet aside and look at the receipts. The Google Fitbit Air launch details put it at $99.99 (£84.99 in the UK, AU$199 in Australia). The Apple Watch Ultra 3 starts at $799. That is close to eight times the price for a device that, on this run, was beaten by 3 beats per minute and 25 calories.
- 8x the cost separates the two wearables at list price.
- 3 bpm is the entire heart-rate gap the extra money buys back.
- 400 meters is what the buyer gives up on distance by going screenless and GPS-free.
What Apple Charges For
The premium is not imaginary. The $799 buys a Grade 5 titanium case, a 1.98-inch always-on display, satellite messaging, dual-frequency positioning accurate to within a few meters, and the running-form metrics above. For an ultramarathoner or a backcountry hiker, those are not luxuries.
Apple’s heart-rate hardware also pairs an electrical sensor with a third-generation optical reader, the combination that lets it double as an AFib (atrial fibrillation, an irregular heart rhythm) screening tool. That redundancy is part of what you are paying for.
Where the Savings Land
For everyone else, the Fitbit Air covers the daily-health checklist for a tenth of the outlay: 24/7 heart rate, heart-rhythm alerts, blood oxygen, sleep stages, and an AI coaching layer through Google Health Coach, bundled with a three-month Google Health Premium trial. It is the kind of value math that has pulled buyers toward budget bands before, the same instinct behind chasing discounted smartwatch and tracker deals.
The moat around the $799 wrist has not collapsed. It has just narrowed to the buyers who genuinely need satellites and stride data.
Which Wearable Fits Which Runner
The honest read is that this is not a fight, because the two devices answer different questions. The decision comes down to how seriously you track distance.
If you want maps you can trust, pinpoint pace, and technique data to chase a personal best, the Apple Watch Ultra 3, or any dedicated running watch positioned above the Fitbit Air tier, is the safer call. A 400-meter error over 10 kilometers is the kind of thing that quietly ruins a training log, and no amount of borrowed phone signal fully fixes it.
If you mostly want a reliable read on heart rate, calories, sleep, and steps without strapping a slab to your wrist, the Fitbit Air does that job at near-flagship accuracy on the metrics that matter most to casual movers. Its weakness is precisely the thing most people never check. For the rest, an $700 saving buys a lot of running shoes.
The screenless band did not out-track the flagship. It got close enough that, for the average wrist, the price tag now does most of the talking.
Frequently Asked Questions
Is the Google Fitbit Air accurate for heart rate?
Yes. In a side-by-side 10-kilometer run, the Fitbit Air’s average heart rate landed within 3 beats per minute of the Apple Watch Ultra 3, which had matched an electrical chest-strap monitor exactly in earlier testing. Both use optical sensors that read blood flow at the wrist, and the Fitbit’s reading was close enough to trust for everyday workouts.
Does the Fitbit Air have built-in GPS?
No. The Fitbit Air has no onboard GPS and instead pulls location from a paired phone over Bluetooth. In testing this caused it to overestimate distance, logging 10.43 kilometers on a route the Apple Watch Ultra 3, which has its own dual-frequency GPS, recorded as 10.03 kilometers.
How much does the Fitbit Air cost compared with the Apple Watch Ultra 3?
The Google Fitbit Air costs $99.99 (£84.99, AU$199), with a Stephen Curry special edition at $129.99. The Apple Watch Ultra 3 starts at $799, making the Apple device roughly eight times the price of the screenless Fitbit band.
Can the Fitbit Air track running pace reliably?
Only roughly. Because it relies on phone GPS, the Fitbit Air reported a pace about 10 seconds per kilometer faster than the Apple Watch Ultra 3 on the same run, which the tester judged to be an overestimate. It is fine for a casual sense of effort but not for precise pace training.
Does the Fitbit Air have a screen?
No. The Fitbit Air is a screenless tracker in a small pebble form factor, with data viewed in the Google Health app. The trade-off is battery life of up to a week, plus fast charging that delivers a full day of power in about five minutes.
Is the Fitbit Air good enough for serious runners?
For casual runners and all-day health tracking, yes. For serious runners who need accurate distance, pace, and form metrics like stride length and vertical oscillation, no. Those users will be better served by the Apple Watch Ultra 3 or a dedicated running watch with onboard GPS.
