Galaxy Fit3 Band Size Chart: What Fits the SM-R390

The Galaxy Fit3 looks like a small smartwatch, but it does not borrow the Galaxy Watch band system. There is no 20mm quick-release lug underneath: the Fit3 (model SM-R390) uses its own one-click band that releases with a push-button on the underside of the tracker, and Samsung's own support pages treat it as a separate system from every Galaxy Watch ^[1]. That single fact answers most Fit3 band questions, because the 20mm strap that fits a Galaxy Watch4 through Watch7 simply has nothing to attach to here. What Samsung does publish for the Fit3 are exact official Sport Band dimensions, official S/M and M/L wrist ranges for its band lengths, and a step-by-step band-change procedure. This chart collects all of it, with the honest gaps marked where Samsung publishes no figure at all.

Galaxy Fit3 at a glance

One model number covers the whole line: SM-R390, launched 2024, sold in gray, silver and pink gold. Samsung's product pages print the physical specs directly ^{[2] [3]}:

The two weight figures are not a typo. Samsung's European spec page lists 18.5 g with the footnote that the specified weight refers to the body only and excludes the band ^[2]; other regional pages print 36.8 g for the same device ^[3]. The gap between the two is the band and regional rounding, so compare like with like when reading reviews.

The official numbers: Galaxy Fit3 Sport Band dimensions

Since there is no lug width to publish, the hard sizing numbers for the Fit3 come from Samsung's own accessory pages for the Galaxy Fit3 Sport Band (model ET-SFR39, sold in Dark Green and Orange). Samsung prints exact dimensions for both halves of the strap ^{[4] [5]}:

Read those widths carefully, because they answer a different question from the one buyers usually ask. The 22mm and 24mm figures are the widths of the strap body itself, the hole half and the buckle half; they are not a lug width, because the Fit3 has no lugs. The end fittings that click into the tracker are a proprietary shape, which is why a strap can be 22mm wide and still refuse to mount on anything except a Fit3. Samsung states the compatibility line itself on the accessory page: compatible models, Galaxy Fit3 ^[4].

So is the Fit3 band 16mm or not?

Search results and shop guides frequently quote "roughly 16mm" for the Fit3 band fitting. That number is a real third-party measurement, not a Samsung figure: the band retailer guide that popularized it describes the Fit3 (SM-R390) as using a proprietary fitting roughly 16mm wide, and explicitly warns that standard 20mm Galaxy Watch bands, 22mm bands and generic straps will not fit without an adapter ^[8]. Samsung, for its part, publishes no millimeter width for the Fit3 mount anywhere on its product, accessory or support pages; every Samsung source describes the system by name instead, one-click bands with a release button on the underside of the tracker ^[1].

The practical consequence: never filter marketplace listings by "16mm". A listing that says 16mm but was measured for a different tracker will not click in, and a well-made Fit3 band whose fitting is 15.8 or 16.5mm across will. Filter by the words "Galaxy Fit3" or the model number SM-R390, exactly as Samsung's own accessory page does ^[4]. The width question matters on real watches with spring bars, where a millimeter of lug gap decides everything; the watch band size chart covers that system, and it is the system the Fit3 deliberately left behind.

S/M and M/L: the official wrist ranges

When Samsung sizes a band by wrist, it uses two lengths, and the official support page prints both: Size S/M fits 130mm to 190mm wrists, and Size M/L fits 145mm to 205mm wrists ^[1]. A wrist between 145 and 190mm falls inside both ranges, and the same page tells you what to do first: measure your wrist, with a cloth tape or with the string method, wrap a piece of string around your wrist, mark where it meets, and lay it against a ruler to read the circumference in millimeters ^[1]. The full walkthrough of that method, including what to do with no tape at all, is in the wrist measuring guide.

One honest gap: the Sport Band accessory page lists a single size with the fixed dimensions above, not separate S/M and M/L SKUs ^[4]. Samsung's S/M and M/L length ranges govern its official band sizes generally ^[1]; whether a given regional store offers the Fit3 Sport Band in both lengths is a store-listing question, and this chart does not invent an answer for it. If your wrist sits near 130mm or near 205mm, check the size selector on the listing before buying.

Compatibility: Fit3 bands versus every other Samsung band

Samsung's support page is unusually direct about which watches share bands, and the Fit3 appears in none of the shared lists. The 20mm list covers the Galaxy Watch4 through Watch7 generations plus the Classics and the Watch5 Pro; the 22mm list covers the older large cases; the Watch8 series and Watch Ultra are called out as a different dynamic lug system whose bands are not interchangeable with other models ^[1]. Mapping the Fit3 against all of them:

The Gear Fit2 row deserves its own honest-gap note. Samsung documents how the Gear Fit2 band comes off, you pull it, no button, no spring bar ^[1], and its New Zealand support pages direct strap replacement for the Gear Fit2 Pro to a service centre ^[7], but Samsung publishes no official width for the Fit2 mount anywhere we could verify. Aftermarket listings overwhelmingly sell 18mm bands for the Gear Fit2 (SM-R360) and Fit2 Pro (SM-R365), yet that figure never comes from Samsung itself, so it stays out of the table. The same applies to the 2019 Galaxy Fit and 2020 Galaxy Fit2 trackers: their pop-in bands are a different system again, and no first-party width exists for them either.

How to change a Galaxy Fit3 band

The procedure is first-party and simple. Samsung's support page: the Galaxy Fit3 bands are one-click bands, similar to the newest smartwatches; press the release button on the underside of the watch and pull the band out, then push the new band into place on each end ^[1]. The accessory page adds the detail that matters when you do it: the Fit3 has two quick-release buttons, one on each side at the back, and both need to be pressed to replace both halves of the band ^[5]. No tools, no spring-bar fork. Contrast that with the Gear Fit2, where the official instruction is to tug the band off and hook the new one back in ^[1], and with classic 20mm quick-release bands, where a spring bar does the locking; the spring bar guide covers that older world if you are coming from it.

Buying a replacement: sport, metal or original

For original bands, the official Sport Band line is the accessory Samsung sells for the Fit3, in Dark Green and Orange, with the dimensions in the table above ^[4]; the band in the box with a new tracker matches its gray, silver or pink gold colorway ^[3]. For third-party bands, silicone, woven and metal options all exist, and the buying rule does not change with the material: the listing must name the Galaxy Fit3 or SM-R390, because the one-click fitting is the part that has to match, not the strap width or the material ^[8]. A metal link band for the Fit3 is still a Fit3-fitting band. What you cannot do is adapt your way in with a generic 16mm strap, because there are no lugs to thread it through ^[8].

How to size a Fit3 band in three steps

First, measure your wrist circumference with a tape or the string method ^[1]; the measuring guide walks both. Second, compare the reading against the official lengths: S/M covers 130-190mm and M/L covers 145-205mm ^[1], and where a single-size Sport Band is the only option, its fixed 122mm hole half plus 93mm buckle half defines how short and long it can close ^[4]. Third, buy by model designation, Galaxy Fit3 or SM-R390, and treat any millimeter width in a listing as descriptive, not as the compatibility key ^[8]. How snugly the tracker should then sit is a sensor question as much as a comfort one, and the general answer is in how a watch should fit.

Honest gaps

This chart carries only figures Samsung prints on its own pages, plus one clearly labeled third-party estimate. Missing on purpose: an official lug width for the Fit3 mount (none exists; the roughly 16mm figure is third-party ^[8]), an official S/M and M/L size split for the Fit3 Sport Band accessory (the page lists one size ^[4]), an official Gear Fit2 or Fit2 Pro band width (not published; the 18mm aftermarket consensus is not first-party), and any official sizing for the 2019 Galaxy Fit and 2020 Galaxy Fit2. Where a seller quotes a number for these, treat it as the seller's measurement.

Related guides

The Fit3's bigger siblings are covered in the Galaxy Watch band size chart, which maps the 20mm Watch4-through-Watch7 generations, the 22mm classics and the Watch8 and Ultra dynamic lug systems. For how rectangular trackers are sized by case height instead of lug-to-lug, see the smartwatch sizing guide. Two other lines that abandoned lug widths entirely: the Pixel Watch band size chart, where bands are picked by official wrist ranges, and the WHOOP band chart, which has no watch head at all. The watch band size chart covers the standard-width world the Fit3 left behind, and the Huawei and Xiaomi charts cover the Fit3's closest tracker rivals, including the Huawei Watch Fit line whose similar name causes constant confusion.

Sources

1. Samsung Support, "How to change the band on your Samsung smart watch" (answer ANS10003740): Fit3 one-click bands with the release button on the underside of the tracker; Gear Fit2 pull-off band change; the official 20mm model list (Watch4/4 Classic/5/5 Pro/6/6 Classic/7, Active2, Active, Watch3 41mm, Watch 42mm); the 22mm list (Watch3 45mm, Watch 46mm, Gear S3); Watch8 series and Watch Ultra dynamic lug system not interchangeable with other models; S/M 130-190mm and M/L 145-205mm wrist ranges; string measuring method. samsung.com/us/support/answer/ANS10003740
2. Samsung Ireland, Galaxy Fit3 gray Bluetooth (SM-R390NZAAEUB) product page: SM-R390 model number, 1.6" (40.0mm) AMOLED 256 x 402 display, 42.9 x 28.8 x 9.9 mm body, 18.5 g weight with the body-only footnote. samsung.com/ie
3. Samsung Canada, Galaxy Fit3 silver Bluetooth (SM-R390NZSAXAC) product page: matching 42.9 x 28.8 x 9.9 mm dimensions, 36.8 g as printed regionally, gray / silver / pink gold colorways, Galaxy Fit3 Sport Bands sold separately. samsung.com/ca
4. Samsung accessory page, Galaxy Fit3 Sport Band Dark Green (ET-SFR39MGEGWW): hole band 22 x 122 x 9.5 mm, buckle band 24 x 93 x 9.5 mm, 18.7 g, fluoroelastomer, Dark Green and Orange shades, compatible models Galaxy Fit3. samsung.com/id
5. Samsung India accessory page, Galaxy Fit3 Sport Band Dark Green (ET-SFR39MGEGIN): same dimensions, plus "Galaxy Fit3 has two quick release buttons, one on each side at the back, that need to be pressed to replace both sides of the band." samsung.com/in
6. Samsung Support, "Galaxy Fit3 features and specs" (answer ANS10004550): 208mAh battery, 13-day typical life, 16MB + 256MB memory, IP68, sensor list. samsung.com/us/support/answer/ANS10004550
7. Samsung New Zealand support, "Gear Fit2 Pro: How do I wear the Gear Fit2 Pro correctly?": buckle-and-pin wearing instructions and strap replacement via a Samsung Service Centre. samsung.com/nz
8. Astra Straps, "Best Galaxy Watch Fit3 Bands: Complete Buyer's Guide" (third-party retailer guide, used only as corroboration and for its clearly labeled own measurement): "The Galaxy Fit3 (SM-R390) uses a proprietary ~16mm band with a one-click push-button attachment. Standard 20mm Galaxy Watch bands, 22mm bands, and generic watch straps will not fit without an adapter." astrastraps.com