The best smart rings for large and small sizes, from size 4 to size 15

What to know before you shop at either end of the range

If your fingers are big or small, the first question isn't which ring is best. It's which rings are made in your size at all. Oura's current ring, the Ring 5, runs from 6 to 13. Its predecessor, the Ring 4, runs from 4 to 15. RingConn's Gen 3 reaches 15; its Gen 2 stops at 14. That spread decides your shortlist before price, battery or accuracy ever come up.

Three things make shopping at the edges harder than it looks:

• Sizes are brand-specific. No brand says its sizes match another brand's, and several say their sizes differ from standard jewelry sizes. A “14” in one brand isn't a 14 in another. Our guide to smart ring sizing compared quotes every brand on this.
• Ranges change between generations. Oura went from 4-15 on Ring 4 to 6-13 on Ring 5, and Ring 5's “redesigned interior fits differently than Oura Ring 4” ( Oura). A newer ring can drop your size.
• Battery changes with size. Oura and Samsung both say battery life depends on ring size. Smaller rings have less room for a battery, and the numbers below show it.

This page is for readers at the ends of the scale. If you sit comfortably in the middle, our best smart rings without a subscription ranks the rings on cost and evidence instead.

Which ring comes in your size

Every ring we cover, with the sizes its maker lists. “Yes” means the brand sells that size in its own sizing system; it says nothing about how that size compares with another brand's.

Sources: Oura's sizing page (Ring 5: 6-13; Ring 4: 4-15; whole sizes only), Samsung's newsroom (“now range from sizes 5 to 15”), RingConn (“Gen 3 now offers 10 sizes, ranging from 6 to 15”; Gen 2 and Gen 2 Air 6-14), Ultrahuman's buy page (5-14) and Circular's shop page (US 6 to 14). Every source is listed at the end of this page.

The quick read: size 13 is universal. Every ring we cover makes one, and it's the top of Oura Ring 5's range. Size 14 rules out only the Oura Ring 5. Size 15 narrows the field to three: RingConn Gen 3, Galaxy Ring and Oura Ring 4. Size 5 gives you three: Galaxy Ring, Ultrahuman Ring PRO and Oura Ring 4. Size 4 leaves one.

Here are the six picks with the specs that matter at the edges of the range:

Battery life changes with size

A ring is a tiny battery wrapped around your finger, and a bigger ring has room for a bigger one. The brands that publish this say it plainly:

• Oura: Ring 5 claims 6-9 days “depending on ring size and usage”. For Ring 4, Oura says “Battery life and longevity depend on Oura Ring size, Oura App settings, feature configuration, activity, battery age, usage, and many other factors” (Oura Support). Oura's safety page gives the capacity range: a 15 mAh battery at US size 6 up to 22 mAh at US 13 (Oura).
• Samsung: “up to 7 days” applies to sizes 12 and 13; smaller sizes get “up to 6 days” (Samsung US). Samsung's footnote doesn't give a figure for sizes 14 and 15. GSMArena's reviewer got about 5 days from a size 11.
• RingConn: we found no battery figure by size. RingConn does publish weight by size for Gen 3: “Size 6 weighs 2.5g, size 15 weighs 3.5g” (RingConn).
• Ultrahuman: no battery figure by size either, but its spec table lists Ring PRO at 3.3 to 4.8 g and says the thickness “varies by size.”

What that means for you: if you wear a small size, plan on the low end of any claimed range. If you wear a 14 or 15, you may do better than the headline figure, but no brand promises it for those sizes. Our smart ring battery life guide reads every claim with its fine print, and a charging case makes a small ring's shorter runtime easier to live with; see chargers and charging cases.

How we ranked them

This page answers one question first: will a ring come in your size? So we ranked on size coverage, weighted toward the ends of the scale (4, 5, 14 and 15), then on what the ring costs to own and which phones it works with. Behind that sits our usual ring rubric, which scores cost of ownership, accuracy evidence, battery, sizing and fit, data ownership and phone support; the weights are on our methodology page. We haven't worn or tested these rings. Sizes, battery figures and fees come from each brand's own pages, linked below.

That's why the order here differs from our overall rankings. The RingConn Gen 2 scores highest on our rubric (8.2), but ranks fifth because its range stops at 14 and starts at 6. The Oura Ring 4 has the widest range of all, 4 to 15, and it's the only ring we cover in size 4. It ranks third rather than first because it needs Oura's membership and because Oura no longer lists it among its current rings, so your size depends on remaining stock. The Galaxy Ring sits second because it covers 5 through 15 with no fee, held back by one hard limit: no iPhone.

The picks in context

1. RingConn Gen 3: sizes 6 to 15, no fee

The best answer for large fingers if you won't pay a subscription. RingConn says “Gen 3 now offers 10 sizes, ranging from 6 to 15” ( RingConn blog), it works with iPhone and Android, and RingConn's free kit arrives before the ring, which ships only after you confirm your size. Those sizes are Gen 3's own: RingConn says they “differ from other RingConn rings,” so a Gen 2 owner has to re-size. RingConn claims up to 14 days a charge (11-14 on its features page) and 150+ days with its charging case; The Gadgeteer's reviewer got about 10 days with vibration alerts on. The weaknesses: we found no published validation of Gen 3 itself, and it showed “Out of stock” on RingConn's own store when we checked, though it was listed on Amazon. It also starts at 6, so small fingers should look further down. More in our RingConn Gen 3 review.

2. Samsung Galaxy Ring: sizes 5 to 15, Android only

The widest no-fee range we found: eleven sizes from 5 to 15, after Samsung added sizes 14 and 15 in January 2025 (Samsung Newsroom). It includes a charging case and has no subscription. The catches are big ones. It doesn't work with iPhone at all, and Double Pinch and Find My Ring don't work on other Android brands. At the small end, Samsung rates sizes below 12 at up to 6 days, and GSMArena got about 5 from a size 11. At the large end, Samsung's US page still describes a 9-size sample kit running 5 to 13 even though it also says the kit now includes the two new sizes, so check before you order a 14 or 15. We couldn't confirm per-size stock on Samsung's US store. We also found no peer-reviewed validation of this ring. See our Galaxy Ring review.

3. Oura Ring 4: sizes 4 to 15, with a membership

If you need a size 4, this is the only ring we cover that makes one, and it also runs all the way to 15: twelve whole sizes, with a matching Ring 4 sizing kit. It's also the ring with the strongest independent evidence behind it. Dial et al. (2025) tested Oura Gen 4 against a Polar H10 chest strap over 536 nights in 13 adults and found resting heart rate error of about 2% and HRV error of about 6% (Dial et al.; a small sample, nighttime resting data only, funded by the US Air Force Research Laboratory with no competing interests declared). The costs: Oura's membership for full features, a typical 5-8 days per charge, and batteries excluded from the one-year warranty. Oura no longer lists Ring 4 among its current rings, though the product page is live and Gizmodo reported Amazon clearance pricing after Ring 5 launched. Our Oura Ring 4 review covers it in full.

4. Ultrahuman Ring PRO: sizes 5 to 14, no fee, pre-order

Ten sizes from 5 to 14, a free sizing kit Ultrahuman says you don't need to return, and no required fee. Ultrahuman claims up to 15 days a charge and up to 45 with the included PRO Charging Case, the longest figures we found. For small fingers it's one of three rings in size 5. The practical problems: in the US it's a pre-order from Ultrahuman's own store (“ships October 10th onwards” when we checked, after earlier dates slipped), it isn't sold on Amazon.com (only its sizing kit is), and we couldn't find its phone requirements published. Its only accuracy data is an in-house pilot on the older Ring AIR, which isn't sold in the US. Customs ruling H354023 cleared the redesigned Ring PRO for import in March 2026. Read our Ultrahuman Ring PRO review before you pre-order.

5. RingConn Gen 2: sizes 6 to 14, no fee

Our top-rated ring overall, ranked fifth here purely on range: 6 to 14, one size short of Gen 3 at the top. If you're a 14, it's a strong choice. No subscription, 10-12 days a charge plus an included case RingConn rates at up to 150 days, iOS 17+ and Android 10+, and a free sizing kit. The Gen 2 Air uses the same sizes (“The ring sizes for both Gen 2 and Gen 2 Air are the same”) if you want the lower-priced version without the case. Gen 2 also has the only chest-strap comparison of any no-fee ring, a 2026 preprint (Tao et al., not peer-reviewed) that found a heart rate bias of -0.42 bpm against a Polar H10 in seated athletes. See our RingConn Gen 2 review and Gen 3 vs Gen 2.

6. Oura Ring 5: sizes 6 to 13 only

Oura's current ring has the narrowest range on this page: 6 to 13. Oura calls it its “slimmest, lightest ring yet,” from 2 grams depending on size, with 6-9 days per charge “depending on ring size and usage.” If you're a 14 or larger, or a 5 or smaller, it's out. And because Ring 5 fits differently from Ring 4, a Ring 4 owner in size 6 through 13 still needs to re-size. It needs the same membership as Ring 4. It's on this list for completeness: most people searching for large or small sizes are asking whether Oura's newest ring fits them. Our Oura Ring 5 review and Oura Ring 4 vs 5 go deeper.

For every spec on every ring in one table, see the smart ring comparison chart.

If you need a size 14, 15 or larger

For size 15, you have three rings: RingConn Gen 3, Samsung Galaxy Ring and Oura Ring 4. If you won't pay a fee and you use an iPhone, that's one ring: the RingConn Gen 3. For size 14, the field opens to the Ultrahuman Ring PRO, RingConn Gen 2 and Gen 2 Air, and the Circular Ring 2 as well.

We found no ring among those we cover offered above size 15. If your finger measures larger than the biggest sizer, our suggestion is to try the largest sizer on a different finger before giving up: Oura says its ring can go on any finger, and RingConn recommends the index, middle or ring finger. Our guide on which finger to wear a smart ring on covers what each brand advises.

Two upsides at the large end: more room for a battery (Oura's largest listed capacity, 22 mAh, is at size 13) and, for Samsung, the top battery claim applies to sizes 12 and 13. The trade-off is weight, though it's small: RingConn's size 15 Gen 3 is a gram heavier than its size 6. For more on picks for bigger hands, see our best smart rings for men.

If you need a size 4 or 5

Size 4 has exactly one option among the rings we cover: the Oura Ring 4, with its membership. For size 5, add the Samsung Galaxy Ring (Android only) and the Ultrahuman Ring PRO (US pre-order). Every RingConn ring, the Circular Ring 2 and the Oura Ring 5 start at 6, and Circular says its sizes run about half a size above standard, so its smallest size is roomier than the number suggests.

Expect less battery. Samsung rates sizes under 12 at up to 6 days rather than 7, and Oura's battery capacity drops to 15 mAh at size 6, per its safety page. A small ring is also where a charging case earns its keep. Our best smart rings for women covers the smaller end of the market in more depth.

What to check before you order at either end

1. Your size in that brand's system. Use the brand's own kit. Our smart ring sizing guide explains how, and why your jewelry size is the wrong starting point.
2. That the kit includes your size. Samsung's US page still carries old 5-to-13 kit wording; confirm before you order a 14 or 15.
3. That your size is actually in stock. Edge sizes are the first to run out. We couldn't confirm Samsung's per-size US stock, RingConn Gen 3 showed “Out of stock” on RingConn's store, and Oura Ring 4 stock is whatever remains.
4. The battery claim for your size. Samsung and Oura both tie battery life to size.
5. The return window. If the edge size still fits wrong, returns are your fallback. Our warranty and returns guide compares them.

Size-range mistakes

• Buying the widest range without checking your phone. The Galaxy Ring covers 5-15 but won't pair with an iPhone.
• Assuming Ring 5 fits like Ring 4. Oura cut the range to 6-13 and changed the interior.
• Reading one brand's 15 as another's. No brand publishes a cross-brand equivalence.
• Sizing up “to be safe.” A loose ring reads worse; RingConn warns the wrong size “may affect comfort and sensor accuracy.”
• Forgetting the fee. The only ring in size 4 comes with a membership that runs as long as you use it.