Fitbit · 2017
IonicSize, Dimensions & Wrist Fit
The Fitbit Ionic sits best on flat wrist widths of about 41–55mm (≈ 10.9–14.7cm wrist circumference). Adjust the slider below to check your wrist.
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The Ionic in short
The figures that decide whether this watch suits you, pulled out of the full specification sheet further down.
- Between 10 hours and 5 days per charge depending on the power mode — smartwatch at best, gps at worst.
- Water rated to 50 m.
- 30g on the wrist. Lighter than 78% of the 39mm watches we have weights for.
- 1.42 inches LCD display, always-on capable.
Does the Ionic fit your wrist?
Drag the slider to your wrist width and see the Ionic overlaid at true scale. Lug-to-lug — not case diameter — decides whether a watch overhangs your wrist.
Watch Fit Tool
For sports watches, lug-to-lug (L2L) is what matters most — it decides whether a watch overhangs your wrist. Bulky is fine; overhang is not.
Measure at the point where you wear your watch — typically just below the wrist bone.
Flat width — lay your arm on a table, palm facing up, and measure straight across the top of your wrist with a ruler. Bone to bone; do not follow the curve down the sides.
Around — wrap a tape measure snugly round the wrist. No tape? Wrap a strip of paper, mark the overlap and hold the strip against a ruler.
Width ≠ circumference. They are different numbers — around 170mm is about 64mm across — so set the toggle to whichever one you actually measured before you type it in.
Fitbit Ionic
Case 38.6mm · Lug-to-lug ~44.4mm · Thickness 12.2mm · 30g
Balanced Fit
44.4mm on a 55mm wrist
Comfortably inside the edges of your wrist, and it seats and sits low enough to wear without thinking about it.
On a 55mm wrist the sweet spot is 47–53mm lug to lug. This one is 44.4mm, so you could go bigger.
Measure where you wear it, just below the wrist bone. Either of these works — the tool converts between them.
- 1. Flat width — arm flat on a table, palm up. Measure straight across the top of the wrist, bone to bone, ignoring the curve down the sides.
- 2. Around — a tape, or a strip of paper marked and held against a ruler, snug the whole way round.
Leather: Attaches at the lugs, so the case back rests on your skin. Thins and softens with wear. Typical figures, not this model’s own.
- No published lug-to-lug for this watch — the span is estimated at 1.15× the case, which is the usual ratio but not a measurement.
Show the measurementsHide the measurements
- Across the wrist5.3mm spare each side
Comfortable, with visible skin either side.
- Off the wrist12.2mm off the skin
Normal sports-watch height for a wrist this size. (12.2mm case, back against the skin)
- How it seats~3.0mm under the rim
Seats well, with the case back following most of the wrist.
- Weight on the wrist30g
Light enough to forget you have it on. (0.5g per mm of wrist)
Happy with the fit? Check current availability for the Ionic.
Check offer2D Dimension Schematics
The Ionic drawn to scale — from above, and in profile against the wrist.
- Fitbit Ionic38.6mm · 12.2mm thick
3D preview
Fitbit Ionic on a wrist
On an arm sized to your own wrist — the view a product photo never gives you.
Shapes are built from published measurements, not manufacturer 3D models — accurate proportions, generic dial.
How long the Ionic lasts, by power mode
Runtime changes by a factor of 12 depending on what you leave switched on. Bars are scaled against the longest mode.
- Smartwatch5 days
- GPS10 hours
How the Ionic ranks on battery
Against the 10 Fitbit watches in our database, ranked on each figure Fitbit publishes.
- Everyday use5 days#6 of 10
Ionic specifications
The figures that decide a purchase, followed by every line Fitbit publishes.
- Battery life
- 5 days
- Display
- 1.42 inches
- Resolution
- 250 x 348 px
- Water rating
- 5 ATM
- Storage
- 2.5GB
- Charging
- 2 hours
Full specification sheet
74 published lines across 8 groups, unedited
Design
- width
- 38.6
- weight
- 30 g
- thickness
- 12.2
- ATM rating
- 5 ATM
- resolution
- 250 x 348 px
- screen size
- 1.42 inches
- Display type
- LCD
- Has a display
- maximum altitude
- 30000 feet
- water resistance
- Waterproof
- Always-On Display
- has a touch screen
- waterproof depth rating
- 50 m
- Watch band is replaceable
- maximum operating temperature
- 45 °C
- has branded damage-resistant glass
- lowest potential operating temperature
- -20 °C
Battery
- charge time
- 2 hours
- battery life
- 5 days
- has wireless charging
- battery life with GPS on
- 10 hours
- has a rechargeable battery
Sensors
- has GPS
- has a gyroscope
- has an accelerometer
- Has a heart rate monitor
- Monitors blood oxygenation levels
Features
- release date
- 2017-09-01
- Has a stopwatch
- Has call control
- Has silent alarm
- internal storage
- 2.5GB
- Has notifications
- Locates your phone
- Has vibrating alerts
Connectivity
- has NFC
- Wi-Fi version
- Wi-Fi 4 (802.11n)
- supports Wi-Fi
- Bluetooth version
- 4
- Is compatible with iOS
- Is compatible with Android
Miscellaneous
- Has passcode
- Has auto pause
- maximum Bluetooth range
- 6.1 m
- Is compatible with Windows
- Is compatible with Mac OS X
- Compatible with smart scales
- has a battery level indicator
- Compatible with external heart rate monitors
App & Software
- Ad-free
- Free app
- Has achievements
- Has goal setting
- Has exercise diary
- Predicts ovulation
- Can be personalised
- Has weight tracking
- Predicts start date
- Tracks water intake
- Has inactivity alerts
- Has period notifications
- Provides activity reports
- Counts how many calories you've burned
Activity tracking
- Measures pace
- Tracks distance
- Tracks elevation
- Tracks your sleep
- Tracks steps taken
- Has exercise tagging
- Has multi-sport mode
- Tracks calorie intake
- Provides sleep reports
- Detects activities automatically
- Has a stroke counter for swimming
Alternatives to the Ionic
Watches that cover a similar amount of wrist, with the measurements that separate them.
Ionic — Frequently Asked Questions
Will the Fitbit Ionic fit my wrist?
The Fitbit Ionic looks balanced on flat wrist widths of roughly 41–55mm (about 10.9–14.7cm circumference). Drag the slider above to check it against your own measurement.
How long does the Fitbit Ionic battery last?
Between 10 hours and 5 days per charge, depending on the power mode. Fitbit rates Smartwatch at 5 days and GPS at 10 hours; the chart above lists all 2 modes.
How does the Fitbit Ionic battery compare with other Fitbit watches?
At 5 days in everyday use it ranks #6 of the 10 Fitbit watches in our database — below the middle of the range. The full ranking, including GPS and power-saving figures, is on our Fitbit battery life comparison.
Is the Fitbit Ionic thick for a 39mm watch?
At 12.2mm, thicker than 74% of 39mm watches — it will sit noticeably high on the wrist. Thickness, not case width, is what decides whether a watch catches on a shirt cuff.
What other watches are the same size as the Fitbit Ionic?
TAG Heuer Carrera Automatic Stainless Steel / Silver - Arabic / Korea, Tissot PRC 100 Solar Quartz 39 Stainless Steel / Ice Blue / Bracelet, Apple Watch Series 11 - GPS + Cellular · Aluminium · 46mm, Xiaomi Redmi Watch Move all sit within half a millimetre of the Fitbit Ionic's 38.6mm case, so they cover the same amount of wrist.
