Oura Ring Sizing Guide: How to Find Your Perfect Fit

Getting the right size is critical for Oura Ring accuracy — a loose ring gives unreliable readings. Here's everything you need to know to find your perfect fit.

Which finger should you wear Oura Ring on?

Oura recommends wearing the ring on your index finger for the most accurate readings. The sensors on the inside of the ring need to sit against the palm side of your finger.

You can wear it on other fingers — middle or ring finger also work — but avoid the pinky finger as it tends to be too small for accurate sensor contact. The index or middle finger gives the best blood flow readings.

Oura Ring sizes

Oura Ring comes in sizes 6 through 13 (US ring sizes). The sizing corresponds to the internal diameter of the ring:

Size	Internal diameter
6	16.5mm
7	17.3mm
8	18.2mm
9	19.0mm
10	19.8mm
11	20.7mm
12	21.5mm
13	22.3mm

How to get an Oura Ring sizing kit

The most accurate way to find your size is to order a free sizing kit from Oura's website before purchasing. The kit contains plastic sizing rings in all sizes. You wear each size for a day to see how your finger changes in size throughout the day (finger size changes with temperature, activity, and time of day).

After wearing the sizing rings for at least 24 hours, you'll know which size is most comfortable during both swelling and natural rest.

How to measure your ring size at home

If you can't wait for a sizing kit, you can estimate your size at home:

1. Wrap a thin strip of paper around your finger at the knuckle (the widest point)
2. Mark where the paper overlaps
3. Measure the length of paper — this is your finger circumference
4. Divide by 3.14 to get the diameter in mm
5. Match to the Oura size chart above

Always measure at the end of the day when fingers are slightly larger. Cold fingers will give a smaller measurement.

What if your size is between two sizes?

Go with the larger size. A ring that's slightly too large is better than one that's too tight. The ring needs to sit snugly but not cut off circulation — you should be able to slide it off without significant resistance, but it shouldn't spin freely.

Oura Ring fit tips

• Your dominant hand fingers are usually slightly larger — if wearing on your dominant hand, check sizing carefully
• Fingers swell during exercise — the ring should still be comfortable during workouts
• If the ring rotates 180° freely, it's too loose and readings will be inaccurate
• The flat edge of the ring should sit on the palm side of your finger

Frequently asked questions

Can I return the Oura Ring if the size is wrong?

Yes. Oura offers exchanges for a different size within 30 days of purchase. However, you can only exchange once, so getting the sizing right from the start saves hassle. That's why the free sizing kit is recommended.

Does Oura Ring sizing match standard ring sizing?

Oura Ring uses US ring sizes (6–13) which correspond to the same internal diameters as standard US jewellery sizing. If you know your US ring size from a jeweller, it should match directly.

How tight should Oura Ring be?

Snug enough that it doesn't rotate freely, but comfortable enough to wear for 24 hours without noticing it. You should see a slight indent when you remove it after a day's wear — this is normal and fades quickly.