Useful estimates, with their limits visible.

These explanations document EveryBand’s independent implementation, reviewed in October 2026. Your installed beta may differ. Publishing a formula or citing research does not establish clinical validation of the app’s sensing or scoring pipeline.

• How EveryBand estimates EnergyEnergy Reserve is a wellness index combining available Recovery, Sleep, Strain and Stress. Calorie expenditure is a separate estimate with different inputs and limits.
• How EveryBand measures HRVEveryBand keeps Apple Health SDNN separate from local nightly RMSSD estimates. Learn how intervals, overnight windows and missing data affect the result.
• How EveryBand calculates RecoveryEveryBand Recovery combines nightly RMSSD, resting heart rate and Sleep with personal history. It needs the current night and two prior complete baseline nights.
• How EveryBand calculates SleepEveryBand Sleep combines duration against estimated need, regularity, efficiency and sleep stress. Stages and missing data have separate limits.
• How EveryBand calculates StrainEveryBand Strain uses covered heart-rate intensity and time, considering movement and steps without counting the same effort repeatedly. Its index can exceed 100.
• How EveryBand estimates StressEveryBand Stress is a 0–100 physiological estimate from heart rate relative to rest, with available HRV context and movement filtering. It does not measure emotions.

EveryBand distinguishes decoded strap observations, imported Health records and values it estimates. Derived Apple Health writes are labeled as estimates and versioned with the EveryBand algorithm revision where Health metadata supports it. The revision belongs to the installed build and may differ across updates.

EveryBand is not a medical device. Outputs may be approximate and must not be used for diagnosis or treatment.

A local nightly RMSSD estimate may be available from admitted strap intervals when quality and coverage gates pass. Generic experimental RR variation is not qualified RMSSD or Health HRV. Local interval-based estimates do not establish verified beat timing, wear state, ECG accuracy or eligibility for Health SDNN export. Definitions and cautious interpretation follow the 1996 ESC/NASPE Task Force standards. Wrist-derived intervals are not equivalent to a diagnostic ECG.

EveryBand’s documented Health HRV input uses SDNN and remains separate from the local nightly RMSSD estimate. The documented Recovery calculation requires nightly RMSSD, resting heart rate, Sleep and sufficient prior nights. Health SDNN does not substitute for RMSSD, so Health input alone does not guarantee a Recovery score. These are different measurements, not interchangeable labels or numbers.

Beat order and wear state are unverified in the ordinal-based local estimation path. Its gated nightly RMSSD estimate is distinct from generic RR variation and from qualified Health HRV. Experimental wellness estimates are independent of official vendor scores and may remain unavailable without completed sleep or sufficient prior nights.

The current TestFlight beta includes optional Apple Health input, with or without a strap. This path uses sleep, HRV (SDNN), resting heart rate and activity already recorded by Apple Watch or other Health sources. It is not a live Apple Watch stream or a watchOS app. Direct strap Bluetooth features remain available.

Health sleep stages may overlap in-bed or awake records. The Health input path resolves overlaps rather than adding every interval together; missing stages are not invented. Resting heart rate is refreshed from available Health records rather than treated as an immutable daily minimum.

Sleep/wake and stage estimates use independent heuristics over wrist activity and available physiological signals. The public actigraphy work in Cole, Kripke, and colleagues (1992) provides background on wrist activity; it does not validate this app or establish that it implements that paper’s algorithm. Recovery uses personal history and requires current nightly RMSSD, resting heart rate and Sleep plus qualifying prior nights. Missing inputs can leave the score unavailable. Read the Sleep and Recovery methods for the actual calculation and limits.

Energy estimates combine demographic inputs, heart rate, and detected activity. The implementation is informed by the public prediction work of Keytel and colleagues (2005) and the reevaluated Harris–Benedict equations. Predictive equations have wide individual error and are wellness estimates, not measured calorimetry.

Strain describes covered activity load on an independent index that can exceed 100; it is not a percentage or WHOOP’s scale. Stress is physiological context, not a measurement of emotion or anxiety. Energy Reserve is a composite wellness index, while calorie expenditure is a separate prediction. The energy explanation covers both.

EveryBand is an independent app and is not affiliated with, endorsed by, or sponsored by WHOOP, Apple, or Bevel. Third-party product names and trademarks belong to their respective owners and are used only for factual compatibility and interoperability descriptions.

Motion artifacts, fit, skin contact, firmware changes, missing samples, physiology, and algorithm assumptions can all affect results. EveryBand’s outputs have not been validated for diagnosis or treatment. Algorithm versions may change, so values from different versions should not be assumed interchangeable.