NHS BMI

NHS BMI Calculator

Calculate adult BMI using NHS-style categories, with context about BMI limits and waist-to-height measurements.

Body Measurements

Add adult height and weight to calculate BMI. The optional waist measurement adds context where it is relevant.

Height unitUse either cm or feet/inches. Unused height fields are ignored.Height

Height feet

Height inches

Weight unitUse the fields that match the selected unit.Weight

Weight stone

Extra pounds

Weight pounds

Age

years

BMI threshold setNHS/NICE use lower overweight and obesity thresholds for some ethnic backgrounds.Context warningBMI can be misleading or unsuitable in these cases.Waist measurementOptional. Enter 0 to skip waist-to-height context.

BMI24.8kg/m2

NHS-style categoryUsually healthy range18.5 to 24.9

Healthy-weight range56.7-76.3 kgFor this height and threshold set

BMI if weight changes

Shows how BMI moves for the same height if body weight changes, with shaded BMI category regions for the selected threshold set.

BMIUnderweightUsually healthyOverweightObesity class 1Obesity class 2Obesity class 3

Current weight against range

Compares the current weight with the lower and upper healthy-weight reference points for the selected threshold set.

Weight

BMI calculation

Height used1.75 m175 cm

Weight used167.6 lb76 kg

Formulaweight kg / height m squared

Threshold setStandard adult thresholds

Context checks

Age enteredAdult categories.35 years

Context warningStill interpret BMI cautiously and alongside wider context.General adult

Waist-to-heightNot enteredNot entered

Reporting useBMI is often requested in health reports, but it is only one measurement.Useful for forms

Assumptions

Calculation notes

Independent calculator using NHS-style adult BMI categories. It is not an official NHS service.
BMI is best treated as one context figure rather than a full health or fitness assessment.
NHS adult BMI tools are not designed for under-18s, pregnancy, eating disorders, or conditions affecting height.
BMI can be misleading for people with high muscle mass because it does not distinguish muscle from fat.
NHS and NICE use lower overweight and obesity thresholds for some Asian, Black African, African-Caribbean, Chinese, and Middle Eastern ethnic backgrounds.
Health concerns, symptoms, eating concerns, pregnancy, or report-specific requirements are best checked with an appropriate health professional.

BMI context

How BMI is calculated, and why it is limited

The calculator gives the report-style BMI number while keeping its health and fitness limitations visible.

BMI arithmetic

The calculator uses adult BMI arithmetic: weight in kilograms divided by height in metres squared.

The chart shows how changing weight affects BMI at the entered height, with category boundaries shaded for context.

BMI formulaBMI = weight kg / height m squared

Report-value example

Example: preparing a report value

Height: 1.75 m
Weight: 80 kg

Result: BMI is calculated from the entered height and weight only.

BMI can be useful for forms and reports, but it does not directly measure fitness, muscle, body fat or health.

What BMI cannot tell you

BMI is notoriously limited, especially for muscular people, older adults, pregnancy and some ethnic-risk contexts.
Use NHS or clinical guidance for health decisions rather than BMI alone.

Content reviewed: 7 September 2026.

NHS BMI guidance How TallyKind works

Guide