Frequently Asked Questions

How long does the battery last?

Several days on a full charge, depending on how often you sync. A full charge takes roughly 90 minutes on the included magnetic dock.

Do I need a subscription?

No. The companion app is free, for iOS and Android, with no monthly fee. Buy the ring once and that's it.

Can I wear it in the shower or the pool?

It handles handwashing, sweat and rain without trouble. We don't recommend swimming laps or hot tubs with it.

Which finger should I wear it on?

Most people use the index or middle finger. Pick the one you measured for, and wear it consistently — switching fingers changes your readings.

How do I know my size?

Measure before you order. Wrap a strip of paper around the base of your finger, mark the overlap, and compare against a standard ring chart. Measure at the end of the day, when fingers are largest. ARO One comes in US sizes 6 to 14. Full instructions are on our size guide.

What if I order the wrong size?

Message us within 30 days and we'll sort out an exchange. See returns for the details.

Is it accurate?

It's accurate enough to show you meaningful trends over weeks — which is what it's designed for. It is not a clinical instrument and shouldn't be treated as one. See our health disclaimer.

Does it track blood oxygen or blood pressure?

ARO One tracks sleep, heart rate trends, movement and activity. We don't market it for blood pressure measurement, because a device making that claim needs regulatory clearance and ours doesn't have it. We'd rather tell you that than imply otherwise.

How long does delivery take?

Typically 10 to 16 business days to the US, with free shipping. Details on the shipping page.

Is my data private?

Your readings live on your phone and in the app account you create. We don't sell personal data. See our privacy policy for specifics.

Will it work with my phone?

Any reasonably recent iPhone or Android phone with Bluetooth will pair with it.