Adult BMI Calculator
Work out adult BMI in kg and cm, lb and ft/in, or stone. See your CDC/WHO category, the NHS thresholds and the healthy weight range for your height.
This calculator gives general information only and is not medical advice. It does not replace a doctor and cannot diagnose any condition. Have a qualified health professional review decisions about your health or diet. Talk to a GP, doctor or registered dietitian about your weight or diet.
Body mass index
General information only, not medical advice or a personal weight goal. No adult category is given under 18. NHS uses adult interpretation at 18–19 while CDC uses age-specific charts through 19. Do not use this tool to assess pregnancy, eating disorders or conditions affecting height. Speak with a clinician about personal health concerns.
Formula checked · NumberSwift · Review process
How this calculator works
Body mass index relates body weight to squared height. It is a screening measurement rather than a diagnosis and does not separate muscle from fat. Standard adult categories follow CDC/WHO cutoffs; the optional NHS adjusted thresholds concern South Asian, Chinese, other Asian, Middle Eastern, Black African and African-Caribbean backgrounds. Age and personal circumstances can change interpretation.
Formula
Metric BMI = kilograms / metres². US customary illustration = pounds / inches² × 703. The displayed value is rounded to one decimal before the illustrative category.
Assumptions & limitations
General information only, not medical advice or a personal weight goal. No adult category is given under 18. NHS uses adult interpretation at 18–19 while CDC uses age-specific charts through 19. Do not use this tool to assess pregnancy, eating disorders or conditions affecting height. Speak with a clinician about personal health concerns.
Sources & reference material
- CDC/WHO: BMI guidance ↗
Published reference used for the stated formula or interpretation; no medical review is claimed.
- CDC/WHO: BMI guidance ↗
Published reference used for the stated formula or interpretation; no medical review is claimed.
- NHS: BMI scope and limitations ↗
Published reference used for the stated formula or interpretation; no medical review is claimed.
- NHS: BMI scope and limitations ↗
Published reference used for the stated formula or interpretation; no medical review is claimed.
- CDC/WHO: BMI guidance ↗
Published reference used for the stated formula or interpretation; no medical review is claimed.
Worked example
At 70 kg and 170 cm, BMI is 70 / 1.7² ≈ 24.22, displayed as 24.2. A CDC illustration of 200 lb and 5 ft 8 in gives approximately 30.4. Neither result alone diagnoses health or body composition.
Our approach to calculations ↗Common questions
Is BMI a diagnosis?
No. It is a screening measure that cannot identify body-fat distribution or distinguish muscle from fat.
Can children use the adult categories?
No. Children and teenagers need age- and sex-specific growth references. Follow the linked CDC or NHS child assessment guidance.
What does the NHS adjusted option mean?
The NHS uses overweight from 23 and obesity from 27.5 for the listed ethnic backgrounds. Below 23, this tool does not invent a separate “healthy” range for those groups.