If you’re upgrading from Ring 4 to Ring 5, your old size is a reasonable guess — not a guarantee. Ring 5’s interior was redesigned to sit slimmer against the skin, and that change can shift how a given nominal size fits. Here’s exactly what changed and how to size correctly instead of assuming your number carries over. (For general sizing principles, see our complete Oura Ring size guide or view the standard Oura Ring size chart).
What Actually Changed Between Ring 4 and Ring 5
Oura Ring 5 uses a redesigned, slimmer interior compared to Ring 4. The sensor housing and internal profile sit differently against the finger, which means the relationship between “circumference measurement” and “how the ring actually feels” isn’t identical across the two generations.
This matters most for people whose measurement lands near a size boundary. If you were solidly in the middle of a size on Ring 4, you’re less likely to notice a difference. If you were between two sizes, the redesign is more likely to tip you toward the other option on Ring 5. (To understand why Oura sizing is different from standard jewelry or how environmental factors like weather affects Oura Ring sizing, check out our dedicated guides).
Size Range: Ring 4 Covers More Ground
Beyond the interior redesign, the two generations don’t even offer the same size range. This alone can be the deciding factor if you’re at either end of the spectrum.
| Oura Ring 4 | Oura Ring 5 | |
| Size range | 4 – 15 | 6 – 13 |
| Half sizes | None | None |
| Interior profile | Standard | Slimmer, redesigned |
| Sizing kit required | Yes, generation-specific | Yes, generation-specific |
If your finger measures at the very small or very large end of the range — near size 4/5 or size 14/15 — Ring 5 may not be offered in your size at all, which makes this less a sizing nuance and more a hard eligibility question.
If You’re Upgrading, Should You Keep the Same Size?
TTreat your Ring 4 size as a starting hypothesis, not the final answer. The most efficient approach is to use the Oura Ring Size to estimate your ideal fit, then request a current Ring 5-specific sizing kit rather than relying on your old Ring 4 sizer.
If your Ring 4 size fit comfortably in the middle of its range, you’re less likely to need a different size. However, if you were between two sizes, it’s worth testing both again. The Ring 5 redesign can be enough to make one size feel noticeably better than the other. (If you’re unsure whether to evaluate a free vs paid sizing kit, compare your options first).
This is also a great opportunity to reassess whether your original size was truly correct. If you’ve simply tolerated your Ring 4 rather than found it genuinely comfortable, use the Oura Ring Size calculator to remeasure before confirming with the official Ring 5 sizing kit. That way, you’re making an informed decision instead of repeating the same sizing guess on a new generation.This is especially crucial if you have large knuckles or frequently debate whether your ring feels too loose or too tight.
First-Time Buyers: Which Generation Should You Size For?
If you haven’t owned either generation yet, size for whichever ring you’re actually purchasing — don’t size for Ring 4 and assume it transfers if you’re buying Ring 5, or vice versa. Use the sizing calculator with the correct generation selected, since the underlying size range and interior profile differ between the two. You can also refer to our international ring size converter guide or read about how Oura compares in Oura vs RingConn vs Ultrahuman.
Before finalizing your choice, ensure you know the best finger for Oura Ring placement, review our Oura Ring care guide, and explore best Oura Ring covers for added protection.
Frequently Asked Questions
Is Oura Ring 5 sizing the same as Ring 4?
Not necessarily. Read our full Oura Ring 4 vs 5 sizing comparison for full details. Ring 5 has a redesigned, slimmer interior, so the same nominal size can fit differently than it did on Ring 4. Treat your old size as a starting point, not a guarantee, and re-measure before ordering.
Can I use my old Oura sizing kit for a new ring generation?
You can use it as a rough reference, but it’s not a reliable final answer across generations, since the interior geometry differs. Requesting a current sizing kit for the specific generation you’re ordering is the more reliable approach.
Which Oura ring has more size options, Ring 4 or Ring 5?
Oura Ring 4 covers a wider range, sizes 4 through 15. Oura Ring 5 is available in sizes 6 through 13 only. If you’re on the small or large end of the range, that availability difference may affect which generation fits you at all.
Should I size up or down when switching from Ring 4 to Ring 5?
There’s no universal rule in one direction – it depends on your individual finger shape and where Ring 5’s slimmer profile lands relative to your knuckle and base measurements. Re-measuring is more reliable than assuming a fixed offset. If you end up with an improper fit, familiarize yourself with the Oura Ring return policy for wrong size exchanges.
This guide is published by Oura Ring Size, an independent sizing resource not affiliated with, endorsed by, or sponsored by Oura Health Oy. “Oura,” “Oura Ring,” “Ring 4,” and “Ring 5” are trademarks or product names of Oura Health Oy, referenced here only to describe compatibility. Interior profile illustrations are simplified for size-relationship reference and are not engineering diagrams. Always confirm your final size with Oura’s official free sizing kit before ordering.
