Pick your device below. Each guide explains exactly what its scores measure, how they're weighted, and where they fall short — so you can read your own numbers correctly.
Apple Watch health metrics: SDNN HRV methodology, Cardio Fitness (VO₂ max) algorithm, sleep stage detection, and AFib History accuracy.
Read guide →How Garmin Body Battery works: HRV-based algorithm, what charges and drains it, score interpretation, and how it compares to Oura Readiness and Whoop Recovery.
Read guide →Google Pixel Watch health metrics: how Fitbit-powered Active Zone Minutes, sleep score, and daily readiness work on Pixel Watch.
Read guide →How Oura Ring calculates Readiness Score, Sleep Score, and Activity Score. Which metrics feed into each, algorithm limitations, and what the numbers mean.
Read guide →What Ultrahuman Home measures in your bedroom — temperature, humidity, light, noise, air quality and snoring — how its Ambient Sleep and Room Scores work, and where it falls short.
Read guide →How the Ultrahuman Ring — Ring PRO, with Ring AIR as the alternative — measures HRV, resting heart rate, skin temperature and sleep, and what feeds its Recovery Score and Sleep Index.
Read guide →How Whoop calculates Recovery score: HRV weighting, resting HR, sleep performance, respiratory rate inputs, and what green/yellow/red actually mean.
Read guide →If you don't know where to start, HRV and Readiness/Recovery scores are the two numbers most wearables emphasize and most people misread. Start with the HRV guide — it explains the metric nearly every device surfaces, regardless of brand.