The Idea
In 2013, Oulu was a city full of unemployed hardware engineers. Nokia's collapse had gutted Finland's phone industry two hours south of the Arctic Circle, leaving behind world-class testing labs and a lot of people who knew how to build sensors. Petteri Lahtela was one of them. He had spent 14 years in mobile and telecoms before switching to IT systems for chronic disease management, where he watched the same thing happen over and over: the health data that mattered reached patients years too late, long after the damage was done.
He kept circling one question. Everyone knows their phone's battery level, so why does nobody know their own? Recovery happened at night, in sleep, and nothing on the market measured it properly. Lahtela also knew the wrist was the wrong place to look. The finger gives a far stronger pulse signal, which means cleaner heart rate variability and respiratory data.
He teamed up with Kari Kivelä and Markku Koskela, both veterans of the Polar and Nokia orbit, and started building a ring.
This was the beginning of Oura.
The Execution
- August 2015: After three years of development, the team put Gen 1 on Kickstarter with a $100,000 goal. They hit it in 15 hours and finished 37 days later on $651,803 from 2,383 backers, half of them in the US and Canada.
- 2016: Kivelä was in a New York Whole Foods when he spotted the first stranger he had ever seen wearing an Oura. It was Harpreet Singh Rai, a hedge fund manager who had lost 50lbs using it. Rai invested, joined the board, and became CEO in 2018.
- November 2017: Gen 2 launched at Slush, shrunk down to a wedding band form factor. It was a genuinely better product, and it still barely sold. Six years in, Oura did around $30 million of revenue in 2019, a rounding error in wearables.
- 2020: The pandemic handed Oura its proving ground. It shipped rings into the NBA bubble and ran a 65,000-person study with UCSF that found continuous finger temperature caught a fever in 76% of cases before symptoms appeared.
- May 2021: A $100M Series C led by Temasek, The Chernin Group and the Dodgers' investment arm valued Oura at $800M. Cumulative rings sold: 500,000.
- October 2021: Gen 3 arrived with the move that changed the model, a $5.99 monthly membership bolted onto a $299 device. Recurring revenue on a one-off purchase. Rai stepped down six weeks later and Tom Hale took over in 2022.
- December 2024: A $200M Series D led by Fidelity, with $75M from glucose monitor maker Dexcom, put Oura at $5.2B on 2.5 million rings sold and roughly $500 million of annual sales, double the year before.
- September 2025: With copycats everywhere, Oura went to war on the form factor and won. The ITC found every asserted claim valid and infringed, banning Ultrahuman and RingConn from the US market. RingConn later settled and took a royalty-bearing licence.
- October 2025: A $900M Series E led by Fidelity doubled the valuation to $11B, on 5.5 million rings sold and revenue on track for $1 billion. Nearly 3 million of those rings sold in that year alone.
- Today: Oura filed confidentially for a US IPO in May and is reportedly targeting a September listing at $16B+, on close to $2 billion of expected 2026 revenue. The open questions: roughly 80% of revenue still comes from hardware rather than subscriptions, and a proposed class action in San Francisco alleges the sleep tracking is less accurate than advertised.
The lesson?
Oura did $30 million in 2019 and $1 billion in 2025. Nothing about the product changed direction in between. What changed was that the world finally showed up to the category, and Oura had spent six unglamorous years being the only company with the sensor in the right place and the patents to prove it. Boring accuracy compounds quietly, then all at once. Build the moat while nobody is looking, because you cannot dig one during the gold rush.