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Anorexic BMI Calculator

BMI against the clinical underweight and severity thresholds.

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The bands at your height

BandBMIWeight

BMI cannot diagnose an eating disorder

The DSM-5 criteria for anorexia nervosa require restriction of energy intake leading to low body weight, an intense fear of gaining weight, and a disturbance in how body weight or shape is experienced. BMI is used only to grade severity once a diagnosis has been made. Atypical anorexia nervosa meets every criterion except low weight and carries similar medical risks, so a normal BMI rules nothing out.

Where to get help

  • Speak to your GP or family doctor — this is the single most useful step.
  • United Kingdom: Beat, the eating disorder charity, runs a helpline and online support.
  • United States: the National Alliance for Eating Disorders operates a daytime helpline.
  • Elsewhere: your national health service or a local eating disorder association.
  • If someone is in immediate danger, contact emergency services.

Body mass index

—

Reference weights

BMI 18.5 (healthy floor)—
BMI 20 (mid-healthy)—
Gap to BMI 18.5—
DSM-5 severity band—

Talk to a doctor

A calculator cannot assess an eating disorder

This page is information, not a diagnosis. Very low weight carries real risks to the heart, bones and hormones that need proper assessment, and refeeding needs medical supervision when weight is severely low. If you are worried about yourself or someone else, please speak to a doctor.

Quick Tool Overview

The Anorexic BMI Calculator compares a BMI against the clinical underweight thresholds and the DSM-5 severity bands used for anorexia nervosa. It is an information tool: BMI is one criterion among several, and it cannot diagnose an eating disorder on its own.

What it does
Places a BMI against underweight and DSM-5 severity bands
You give it
Height and weight in metric or imperial units
You get back
BMI, the band it falls in and a healthy target weight
Best for
Understanding what the clinical thresholds actually are
Calculators Free, unlimited use No sign-up Runs in your browser

About the Anorexic BMI Calculator

Compare a BMI against the clinical thresholds used for underweight and against the DSM-5 severity bands for anorexia nervosa: mild at 17 and above, moderate from 16 to 16.99, severe from 15 to 15.99 and extreme below 15.

BMI is only one of several diagnostic criteria and cannot diagnose an eating disorder on its own — the DSM-5 criteria also require restriction of intake, intense fear of weight gain, and a disturbance in how body weight is experienced, and a person can be seriously ill at a normal BMI. This page is intended as information, and it lists support organisations alongside the result. If you are worried about yourself or someone else, please speak to a doctor rather than to a calculator.

Key features of the Anorexic BMI Calculator

The actual DSM-5 bands

Mild at 17 and above, moderate 16 to 16.99, severe 15 to 15.99 and extreme below 15 — the real thresholds, not approximations.

Says what BMI cannot do

Diagnosis rests on behaviour, fear of weight gain and body image, and atypical anorexia occurs at normal weight.

A target, not just a verdict

The weight corresponding to a BMI of 18.5 and 20 at your height, so the number has somewhere to go.

Support links on the page

Eating disorder organisations are listed alongside the result rather than buried in a disclaimer.

Completely private

Nothing entered here is transmitted or stored anywhere.

How to use the Anorexic BMI Calculator

  1. 1

    Enter height and weight

    In metric or imperial units.

  2. 2

    Read the BMI and band

    Your figure is placed against the underweight thresholds and the DSM-5 severity ranges.

  3. 3

    See the healthy range

    The weight that would put you at a BMI of 18.5 and at 20, for your height.

  4. 4

    Use the help links

    Support organisations are listed on the page. A calculator cannot assess an eating disorder.

Frequently asked questions

Below 18.5 is classified as underweight. Below 17 is generally treated as moderately underweight and below 16 as severely underweight.

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