Calculation library

See What Every Number Means

See how every Body Insights score and health calculation works, what data it reads, what happens when data is missing, and its limits.

Body Insights turns Apple Health data into scores, trends, and plain guidance. Open a calculation to see its inputs, missing-data rules, and limits.

These pages explain each method. Proprietary weights and unsupported medical claims stay out.

Sleep and timing

How Light Exposure Is Calculated

Learn what goes into light exposure, how missing data is handled, and what the result means.

How Metabolic Sleep Is Calculated

Learn what goes into metabolic sleep analysis, how missing data is handled, and what the result means.

How Overnight Recovery Is Read

Learn what goes into overnight recovery, how missing data is handled, and what the result means.

How Your Body Clock Is Estimated

Learn what goes into circadian timing, how missing data is handled, and what the result means.

How Your Sleep Debt Is Calculated

Learn what goes into sleep debt, how missing data is handled, and what the result means.

How Your Sleep Score Is Calculated

Learn how your score and quality message use sleep stages, efficiency, interruptions, and your recent pattern.

Recovery, stress, and energy

Apple Watch Body Battery Score: How It Is Calculated

Learn what goes into body battery, how missing data is handled, and what the result means.

Apple Watch Morning Recovery

Learn what goes into waking recovery, how missing data is handled, and what the result means.

Apple Watch Readiness Score

Learn what goes into readiness score, how missing data is handled, and what the result means.

How Acute Stress Is Detected

Learn what goes into acute physiological stress, how missing data is handled, and what the result means.

How Burnout Risk Is Calculated

Learn what goes into physiological burnout-risk estimate, how missing data is handled, and what the result means.

How Nervous System Age Is Estimated

Learn what goes into nervous system age, how missing data is handled, and what the result means.

How Stress Balance Is Calculated

Learn what goes into stress score, how missing data is handled, and what the result means.

How Your Life Balance Score Works

Learn what goes into life balance questionnaire score, how missing data is handled, and what the result means.

How Your Resilience Score Works

Learn what goes into physiological resilience score, how missing data is handled, and what the result means.

Fitness and cardiovascular

Cardio Adaptability Explained

Learn what goes into cardio adaptability, how missing data is handled, and what the result means.

How Post-Workout Recovery Is Read

Learn what goes into post-workout recovery, how missing data is handled, and what the result means.

How Steps Become a Long-Term Signal

Learn what goes into daily steps and longevity, how missing data is handled, and what the result means.

How Your Fitness Age Is Calculated

Learn what goes into fitness age, how missing data is handled, and what the result means.

How Your Fitness Summary Works

Learn what goes into fitness metrics, how missing data is handled, and what the result means.

How Your Heart Rate Metrics Work

Learn what goes into heart rate metrics, how missing data is handled, and what the result means.

How Your Training Load Is Calculated

Learn what goes into training load, how missing data is handled, and what the result means.

Glucose, metabolism, and fasting

How Fasting Readiness Is Calculated

Learn what goes into fasting readiness, how missing data is handled, and what the result means.

How Metabolic Readiness Is Read

Learn what goes into metabolic readiness, how missing data is handled, and what the result means.

How Workout Glucose Response Is Read

Learn what goes into exercise glucose response, how missing data is handled, and what the result means.

How Your Glucose Overview Is Calculated

Learn what goes into daily glucose metrics, how missing data is handled, and what the result means.

Risk, reports, and personal context

How Genetic Insight Scores Work

Learn what goes into genetic insight score, how missing data is handled, and what the result means.

How Health Anomalies Are Detected

Learn what goes into health anomaly detection, how missing data is handled, and what the result means.

How Illness Risk Is Estimated

Learn what goes into wearable illness-risk estimate, how missing data is handled, and what the result means.

How Your Monthly Health Audit Works

Learn what goes into monthly health report, how missing data is handled, and what the result means.

How Your Morning Report Is Built

Learn what goes into morning health report, how missing data is handled, and what the result means.

Start with the card in front of you

Open a card in Body Insights and tap its information button. The link stays off until its explanation is reviewed and live.

See the calculations behind your health cards

Body Insights turns your Apple Health history into scores you can inspect and use.

Read my Apple Health data