Health-metric references, measurement methodology and calculators, with source support and model limitations described on each page. For people who already own a wearable and want to understand their numbers.
Explore Metrics Library Open CalculatorsDo you use Oura, Ultrahuman, Whoop, or Garmin? Start with the metric that matters most to you.
Oura → Ultrahuman → Whoop → Garmin → See all devices →Definitions, measurement methodology, the reference ranges that have a documented source, and how Oura, WHOOP and other devices measure each metric.
The time variation between consecutive heartbeats. Oura and WHOOP both report a nightly value and advise comparing it with your own history.
View metric →Percentage of time in bed spent asleep. The National Sleep Foundation consensus treats 85% or higher as an appropriate indicator of good sleep quality.
View metric →Maximum oxygen uptake during peak exertion. Oura (Cardio Capacity), WHOOP and others report estimates, not laboratory measurements.
View metric →Beats per minute at rest. Mayo Clinic, citing the AHA, gives 60–100 bpm for an awake pulse check; Oura and WHOOP measure it during sleep.
View metric →Slow-wave sleep, estimated by wearables from movement and heart-rate signals. See what the National Sleep Foundation consensus and the manufacturers say.
View metric →Rapid eye movement sleep, estimated by wearables rather than measured from brain waves. See the documented statements from the National Sleep Foundation, Oura and WHOOP.
View metric →Time it takes to fall asleep. The National Sleep Foundation consensus counts up to 30 minutes as consistent with good sleep quality.
View metric →Breaths per minute during sleep, derived from heart-rate data by Oura and WHOOP. A rise above your own baseline can be a sign the body is under strain.
View metric →Deviation from your personal baseline during sleep, measured at the finger by Oura and the wrist by WHOOP. Skin temperature is not core body temperature.
View metric →Proprietary composite scores (Oura Readiness, WHOOP Recovery) explained — documented inputs, each manufacturer's rating bands, and why they cannot be compared.
View metric →Two calculators compare your value with a published range for the measurement you choose. Three earlier tools are disabled because their reference tables or models had no documented basis.
Disabled: the reference table behind it had no documented source.
Open calculator →Enter time in bed and time asleep. See your efficiency and the National Sleep Foundation consensus limits for your age category.
Open calculator →Disabled: the classification table could not be traced to a source.
Open calculator →Compare a resting heart rate with the range published for the measurement you used: manual pulse, Oura or WHOOP.
Open calculator →Disabled: the model had no documented basis.
Open calculator →Documented ranges and statements with their source, population and measurement. Tables with no documented source have been removed. No paywalls, no email required.
Nyxova does not publish HRV population tables without a documented basis. Read each device against your own history.
View table →Classification tables removed; see what Oura (Cardio Capacity) and WHOOP say about their own estimates.
View table →The documented adult range (60–100 bpm for an awake pulse check), Oura's stated range and WHOOP member averages, each tied to its measurement.
View table →National Sleep Foundation consensus limits for three adult age categories, plus Oura and WHOOP statements.
View table →Documented statements from the National Sleep Foundation, Oura and WHOOP, each with its population and measurement.
View table →Documented statements from the National Sleep Foundation, Oura and WHOOP, each with its population and measurement.
View table →National Sleep Foundation consensus limits for three adult age categories and Oura's own guidance.
View table →The range Oura and WHOOP each quote for healthy adults at rest, and how each derives its nightly figure.
View table →Algorithm explanations, score interpretations, and known measurement limitations — for popular wearables and sleep trackers.
Readiness Score, Sleep Score, and Activity Score — what inputs they use and how they're weighted.
Read guide →Ring PRO (with Ring AIR as the alternative) — Recovery Score, Sleep Index, and Movement Index, and what Ultrahuman does not publish.
Read guide →A bedside sleep monitor for the room — temperature, humidity, light, noise, air quality and snoring.
Read guide →How HRV, stress, sleep quality, and activity combine into the 0–100 Body Battery score.
Read guide →Green / Yellow / Red recovery explained. HRV, resting HR, sleep performance, and respiratory rate inputs.
Read guide →Health app metrics including HRV (SDNN), VO₂ max estimation, sleep stages, and AFib detection.
Read guide →Fitbit-powered metrics — Active Zone Minutes, sleep score, and daily readiness explained.
Read guide →