The short version
Note: the Ultrahuman Ring Air is under a US import ban (October 2025, Oura ITC patent win) and cannot be bought in the US. Ultrahuman’s US-available successor is the Ring Pro — subscription-free, with a ~15-day battery. Read this comparison with that in mind if you are in the US.
Two subscription-free rings at the same overall standing. Ultrahuman Ring Air is the lightest, most open (cross-platform) option, undercut by battery-reliability reports. Samsung Galaxy Ring is the comfortable, well-supported choice — if you live in the Galaxy ecosystem.
When the Ultrahuman Ring Air is the right pick
You are on iPhone or a non-Samsung Android, want the lightest ring, and value a metabolic-leaning app. Accept the battery risk and it is the more flexible buy.
When the Samsung Galaxy Ring is the right pick
You already carry a Samsung Galaxy phone and want a reliable, subscription-free ring that plugs straight into Samsung Health and your Galaxy Watch data.
Also worth comparing
For the accuracy leader (with a subscription), see the Oura Ring 4, or the full field in the best HRV trackers.