Fitbit comparison: which models track HRV, blood oxygen and skin temperature

Short answer

Every Fitbit and Pixel Watch in Google's current vitals table shows heart rate variability (HRV), from old models like Charge 2 and Alta HR to Fitbit Air and Pixel Watch 5 (1). The real differences are elsewhere: blood oxygen (SpO2) and skin temperature are missing on older and simpler models, only some devices have an ECG app or an EDA stress scan, and only some have built-in GPS (1, 2, 3).

For health tracking, the useful split is: Fitbit Air, Charge 6, Inspire 3, Versa 4, Sense 2 and Pixel Watch 2–5 show the full set of overnight vitals in Google's table; Charge 6, Sense 2 and Pixel Watch models add an on-demand ECG (1, 3).

If you've been staring at five comparison charts that all say something different, it's not your fault. Google's own help pages don't fully agree for a few models. We show where, and how to check yours in two minutes.

Note: this article is for general education and is not medical advice. Google says its vitals feature "is not intended to diagnose or treat any medical condition" (1). Chest discomfort, shortness of breath, a cold sweat, or a fast or irregular heartbeat with lightheadedness can be signs of a heart attack: call 911. Features were checked on Google's official pages on November 8, 2026. This guide is published by Welltory, which makes one of the apps mentioned. Google, Fitbit and Pixel are trademarks of Google LLC; Welltory is not affiliated with Google.

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Fitbit health features by model: the comparison table

This table shows the overnight vitals Google says each device supports in the Google Health app (Health → Vitals), plus ECG and GPS. The Fitbit app became the Google Health app in May 2026, so older guides may name menus that have moved (4).

\* Google's two pages disagree for these models; see "Where Google's own lists disagree" below.

How to read the table. A tick means the device can produce the metric, not that it will every night. Most overnight vitals need at least three hours of good-quality sleep, a snug band and a recent sync; skin temperature needs three nights to set a baseline; and SpO2 on some devices needs an SpO2 clock face or app (1).

Which Fitbit measures HRV?

All of them in Google's vitals table, as of November 2026: Fitbit Air, Charge 2 through Charge 6, Inspire 2, Inspire 3, Inspire HR, Luxe, Alta HR, Blaze, the Versa and Sense series, and Pixel Watch through Pixel Watch 5 (1).

How it's calculated. Google uses the RMSSD formula on heart rate data from the optical sensor and shows HRV with a personal range built from up to 30 days of your data (1). RMSSD is the standard short-term measure of beat-to-beat variation and mainly reflects the "rest and digest" side of the nervous system (5).

Does the model change the number? Every model uses the same formula and the same overnight timing, so the method is the same. What can differ is signal quality: band fit, how much you move at night, and sensor generation. We found no independent study that compares nightly HRV between Fitbit models. A 2022 validation of six wearables for sleep, heart rate and HRV didn't include a Fitbit (6).

HRV is free. You don't need Google Health Premium to see HRV, SpO2 or heart rate (7).

What counts as normal? No model gives you a universal "good" number. Our guides to what a good HRV range is and low HRV causes explain how to read yours against your own range.

Which Fitbit measures blood oxygen (SpO2)?

Google's vitals table marks SpO2 for Fitbit Air, Charge 4, Charge 5, Charge 6, Inspire 3, Luxe, the Versa and Sense series, and Pixel Watch 2 through 5 (1). Charge 2, Charge 3, Inspire 2, Inspire HR, Alta HR, Blaze and the first Pixel Watch don't have it.

These devices use red and infrared light at the wrist to estimate overnight SpO2. Google notes that nighttime levels are usually lower than daytime levels, typically above 90% (1). The Charge 6 spec page says SpO2 is "not intended to diagnose or treat any medical condition or for any other medical purpose" and isn't available in all countries (8).

A wrist estimate isn't a pulse oximeter reading. Even medical fingertip oximeters have limits: the FDA has warned that skin pigmentation, poor circulation, cold fingers and nail polish can affect accuracy (9). Our guide to blood oxygen levels explains what the numbers mean.

Which Fitbit tracks skin temperature?

Fitbit Air, Charge 4, Charge 5, Charge 6, Inspire 2, Inspire 3, Luxe, the Versa and Sense series, and Pixel Watch 2 through 5 (1).

It's skin temperature variation: the change in your wrist temperature during sleep compared with your baseline, not your core body temperature and not a fever thermometer. Google lists room temperature, bedding, your circadian rhythm, the menstrual cycle and a possible fever as things that move it (1). The Charge 6 page adds that skin temperature "only displays variation" and isn't available in all markets (8).

If you track your cycle, a temperature trend can help you see patterns across phases. Our guide to menstrual cycle phases covers what typically changes.

ECG, AFib and stress scans: the extras that differ most

ECG app

The Google ECG app records a 30-second reading while you hold your fingers on the device's sensors and sit still. It sorts the result into normal sinus rhythm, signs of atrial fibrillation (AFib) or inconclusive (3). Google lists these devices: Google Fitbit Edge, Charge 6, Charge 5, Sense 2, Sense, and the Pixel Watch series (3).

Limits matter here. Google says the app "can't detect all heart conditions," can't assess rhythm when your heart rate is over 120 bpm or under 50 bpm, and that "only a doctor can diagnose AFib" (3). It's available only in select countries. Our explainer on what an ECG is covers how a wrist reading differs from a 12-lead test.

Passive AFib checks

Some devices also check passively for signs of AFib while you're still or asleep. Google lists this for Fitbit Air and Charge 6 on their store pages (10, 11). For other models, check the Health Guardian or notification settings in the Google Health app. Neither the passive check nor the ECG detects a heart attack.

EDA and stress

Google's data page lists an EDA (electrodermal activity) scan on Charge 6 and all-day Body Response tracking with continuous EDA on Pixel Watch 2 through 5 (2). EDA picks up tiny changes in skin sweat linked to the body's stress response. The Charge 6 page puts it simply: "an EDA scan can share how your body is responding to stress" (11). Our comparison of stress monitoring devices explains what these scores can and can't tell you.

GPS, screen and size: the everyday differences

Health metrics are only half the decision. The other half is whether you'll wear the thing.

• Built-in GPS (pace and distance without your phone): Charge 4, 5 and 6; Sense and Sense 2; Versa 3 and 4; Ionic; Pixel Watch models (2).

• Connected GPS (uses your phone): Fitbit Air, Inspire 2 and 3, Luxe, Charge 2 and 3, Versa, Versa 2, Versa Lite, Blaze (2).

• No screen: Fitbit Air. Its sensor pebble weighs 5.2 g, about 12 g with the band (12).

• Small screen, tracker shape: Charge 6 weighs 30 g and lists up to 7 days of battery (8).

For sleep data, the lightest device you'll keep on at night usually beats the most capable device you take off.

Where Google's own lists disagree

We compared two official Google pages on November 8, 2026: the vitals help page, which shows device support as a table of icons (1), and the product documentation page on what data each device collects (2). They agree on most devices, but not all:

The vitals page notes its own device lists for SpO2 are inconsistent across sections (1). We read the table from its icons, so a misread cell is possible. When in doubt, trust what your own app shows.

How to check your model in two minutes:

1. Open the Google Health app and make sure your device has synced today.

2. Tap the Health tab, then Vitals (1).

3. Look for HRV, SpO2, skin temperature and breathing rate after a night of at least three hours of good sleep.

4. If SpO2 is missing, check whether your device needs an SpO2 clock face or app (1).

5. If skin temperature is missing, wait for three nights of data (1).

6. If something is still blank after a week, the metric probably isn't supported on your device or in your country.

Which Fitbit should you choose for your goal?

Start from the question you want answered, not from the spec sheet.

"I want to know if I'm recovering or run down." Any model with HRV and resting heart rate works, and that's every device in the table. Pick the one you'll wear every night. Fitbit Air is the lightest (12); Inspire 3 and Charge 6 have screens.

"I want to notice when I'm getting sick." Look for HRV, resting heart rate, skin temperature and breathing rate together. Fitbit Air, Charge 6, Inspire 3, Luxe, Versa, Sense and Pixel Watch 2–5 have all four (1).

"I've had palpitations and want to record one." You need an ECG app: Charge 6, Charge 5, Sense, Sense 2, Google Fitbit Edge or a Pixel Watch (3). A recording helps your doctor, but doesn't replace a medical test.

"I want sleep data without a watch." Fitbit Air or Inspire 3. Our comparison of the best sleep trackers covers how accurate wrist sleep data is.

"I run without my phone." Choose built-in GPS: Charge 6, Versa 4, Sense 2 or a Pixel Watch (2).

"I already own an older Fitbit." If it shows HRV and resting heart rate, it already answers the main recovery question. Our guide to whether you need a new wearable walks through the decision.

What's free and what needs Google Health Premium

For every model, the core data is free with a compatible device: heart rate, HRV, SpO2, sleep score, sleep stages, steps and Readiness (7). Google Health Premium costs $9.99 a month or $99.99 a year (7) and renews automatically until you cancel (13). It adds the Gemini-based coach, adaptive plans, detailed sleep insights and a workout library (7).

One caution: Google's own pages aren't consistent about Readiness. The Charge 6 store page says Daily Readiness is "available with Google Health Premium," while the Fitbit Air store page lists a Readiness score among the device's features (10, 11). Check in your app before paying for it. Fitbit Air and Charge 6 include three months of Premium (10, 11); set a reminder if you don't plan to keep it.

Common mistakes when comparing Fitbits

• Buying for HRV. Every model in Google's table already has it (1).

• Comparing HRV across brands. Fitbit uses RMSSD; other brands use other formulas and timing (5). Compare a device only with itself.

• Treating skin temperature as a thermometer. It's variation from your baseline, not core temperature (1).

• Expecting an ECG on every model. Only some devices have it (3).

• Trusting comparison charts from before May 2026. The app and menus changed (4).

• Upgrading before you've worn the old one at night for two weeks. Most of the health value is overnight.

Living with your Fitbit: the questions people ask next

Does Fitbit Inspire 3 track HRV?

Yes. Google's vitals table marks HRV, skin temperature, breathing rate and resting heart rate for Inspire 3 (1). Its SpO2 support differs between Google's pages, so check Health → Vitals in your app.

Does Fitbit Charge 6 track HRV?

Yes. Charge 6 shows HRV, SpO2, skin temperature, breathing rate and resting heart rate in Google's vitals table (1), and it adds an ECG app and an EDA scan (2, 3).

Why don't I see HRV on my Fitbit?

Most overnight metrics need at least three hours of good-quality sleep, a full day and night of wear, a snug band and a recent sync (1). Our guide to HRV during sleep explains why the night matters.

Which Fitbit has the most health features?

On Google's lists, Charge 6, Sense 2 and Pixel Watch 2–5 cover all the overnight vitals plus an ECG app (1, 3). More features don't mean better data for you; fit and nightly wear matter more.

Is an older Fitbit still worth wearing?

Often, yes. If it shows HRV and resting heart rate, it answers the main recovery questions. You'll miss SpO2 and skin temperature on Charge 2 and 3, Inspire HR and Alta HR (1).

Before you blame yourself

Comparison shopping often starts from a feeling: "My tracker says I sleep badly and my HRV is low, so maybe I need a better tracker."

The feeling: "My numbers look worse than other people's. Maybe my device is wrong, or maybe I'm doing everything wrong."

The cause you can often see: HRV varies widely between people of the same age (5), so comparing with others tells you little. Within your own data, late nights, alcohol, hard training and stress usually show up as a lower HRV and a higher resting heart rate on the same mornings.

One lever for one to two weeks: before buying anything, wear the device you have every night for 14 nights and write one line each evening: alcohol yes or no, hard workout yes or no, stress from 1 to 5. Then look for the pattern.

If the pattern is clear, a new device won't change it. If nothing moves after a real change, that's a reason to talk with your doctor, not a failure.

When to see a doctor

A tracker can't diagnose anything. See a doctor if:

• Your ECG app shows signs of AFib, or you get an irregular rhythm notification.

• You feel a fast, pounding or irregular heartbeat, especially with dizziness.

• Your resting heart rate stays well above your usual level for more than a week without a clear reason.

• You feel short of breath or unusually tired along with low SpO2 trends.

• You snore loudly, stop breathing or gasp in your sleep, or feel sleepy every day.

• You faint or nearly faint.

Call 911 if you have possible heart attack symptoms: chest discomfort, discomfort in other areas of the upper body, shortness of breath, a cold sweat, nausea or lightheadedness (14). Google's ECG app can't detect a heart attack (3).

How to bring this up with your doctor

What to ask for, by name. After an AFib result: "Can we confirm this with a 12-lead ECG, and would a monitor I wear for a few days help?" With snoring and low SpO2 trends: "Should I have a sleep study?" With a resting heart rate that stays high and fatigue: "Could we check thyroid function and a basic blood panel?"

What to bring. The ECG PDF or screenshot from the Google Health app, two to four weeks of resting heart rate, HRV and sleep, and your device model. Say that wrist SpO2 and HRV are estimates from an optical sensor.

What to say if you're brushed off. "I know a tracker isn't a diagnosis. I'm asking whether these symptoms, with this pattern, are worth one proper test."

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How Welltory helps — and what it cannot do

The limits first. Welltory is a general wellness product, not a medical device. It doesn't diagnose heart conditions or any other illness, and it doesn't replace your doctor or your device's own notifications.

Fitbit and Pixel Watch HRV stay in the Google Health app. Welltory doesn't use HRV from Fitbit or Google Pixel Watch: its compatibility page marks both for activity tracking, not HRV measurements, and notes that the direct Fitbit connection is for Welltory Premium users (15). Welltory Premium is a paid subscription that renews automatically until you cancel. Fitbit sleep, heart rate, workouts and steps can also reach Welltory through Health Connect on Android or Apple Health on iPhone; Welltory recommends using one connection type, not both (16).

Sleep next to your other data on Android. Sleep Analysis can use Fitbit sleep from Health Connect to build a sleep score (17).

A separate HRV spot reading. On phones where the camera and flash sit close together, you can take a short HRV and heart rate reading with your fingertip — a deliberate spot measurement, not continuous monitoring. It doesn't work on Google Pixel phones (18). Our guide to measuring HRV without a wearable explains how. Compare camera readings only with each other, not with your Fitbit's overnight number.

A record for your doctor. From the web app, you can export your data as CSV: Dashboard → choose a chart → pick the time range → Export (19).

How we made it

We based this comparison on the Google Health Help Center pages on vitals, the ECG app and the move to the Google Health app, Google's product documentation on Fitbit and Pixel Watch data, Google's store pages for Fitbit Air and Charge 6, the Google Health Premium page, launch coverage from 9to5Google and Droid Life, a review of HRV metrics, a validation study of six wearables, the FDA's pulse oximeter brief and the American Heart Association's warning signs page. We compared Google's two device lists line by line and flagged where they differ. Device features were checked on November 8, 2026. Search questions came from what people in the United States most often ask when they compare Fitbit models. For the product section, we checked every function against the Welltory Help Center on November 8, 2026.

Made with AI tools, then edited and fact-checked by the Welltory team. See our Editorial & AI policy.

Jane Smorodnikova, co-founder of Welltory, built the methodology behind how we read physiological data.

Written by Tatsiana Yashyna.

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