Apple Health metrics › Body Mass Index (BMI)

Body Mass Index (BMI) on Apple Watch and iPhone

A quick screening ratio of weight to height.

What it is

BMI is a coarse tool. It ignores muscle and fat distribution but is simple to track.

How Apple measures it

Apple Health calculates it from your height and weight entries.

What's a normal range?

The WHO classes 18.5 to 24.9 as normal, 25 to 29.9 as overweight and 30 and above as obesity. Athletes with high muscle mass can read high without excess fat.

What moves it

• Weight changes
• Muscle mass
• Height entry accuracy
• Age and ethnicity differences
• Measurement frequency

See Body Mass Index (BMI) next to your other vitals

Apple Health keeps this number several taps deep. OnlyVitals puts the metrics you pick, including Body Mass Index (BMI), on a single dashboard so you can read them at a glance. Everything stays on your device.

Frequently asked questions

What is a normal BMI?

18.5 to 24.9 for adults, per the WHO. It is a screening guide, not a diagnosis.

Is BMI accurate for athletes?

Often not. Muscle weighs more than fat, so body fat percentage and waist measurements are better for muscular people.

Related metrics

• Body Fat Percentage
• Resting Heart Rate
• Heart Rate Variability (HRV)
• VO2 Max (Cardio Fitness)
• Blood Oxygen (SpO2)
• Respiratory Rate

This page is general information, not medical advice. Ranges vary by age, sex, fitness and device. Talk to a clinician about anything that worries you.