Precision Utility
Ideal Weight
Calculator
Data
3 Formulas
Source
NHS + Clinical
Find your ideal weight using three trusted methods. Enter your height and sex — the calculator compares the NHS BMI-based healthy range, the Hamwi formula and the Devine formula side by side. Built for anyone looking for a quick, evidence-based weight reference.
Your Measurements
NHS Healthy Weight Range
53.5 – 72.0 kg
NHS Range
53.5 – 72.0 kg
Hamwi Formula
70.3 kg
Devine Formula
73.0 kg
BMI Range
18.5 – 24.9
How the ideal weight calculator works
Start by entering your height in centimetres and selecting your biological sex. The calculator converts your height to metres and inches internally so it can run all three formulas at once.
The NHS healthy weight range multiplies your height in metres squared by the lower and upper BMI boundaries (18.5 and 24.9) to produce a weight range in kilograms. If your weight falls inside this range, the NHS considers you a healthy weight.
The Hamwi formula uses a base weight for the first five feet of height, then adds a fixed increment for every additional inch — 2.7 kg per inch for men, 2.2 kg per inch for women. The Devine formula works similarly but uses 2.3 kg per inch for both sexes, with different base weights.
You get all three results side by side so you can compare. No single formula is perfect — viewing them together gives a more balanced picture of where a healthy weight might sit for your frame.
What you need to know about ideal weight
No single number defines your "ideal" weight. These formulas provide clinically-informed estimates, but several factors mean the right weight for you may differ from the calculated values.
Key considerations:
- BMI limitations — BMI does not distinguish between muscle and fat. Athletes and people with high muscle mass may show an "overweight" BMI while being in excellent health
- Frame size — People with naturally larger or smaller bone structures will sit at different points within a healthy range. Wrist circumference is sometimes used as a rough frame-size indicator
- Muscle mass — Resistance training increases lean mass, which weighs more than fat. A body composition measure like body fat percentage gives a clearer picture than weight alone
- Multiple formulas — Hamwi and Devine were developed decades ago for clinical dosing and screening. They remain widely used but were not designed for every body type. The NHS BMI range is broader and accounts for more variation
- Ethnicity — The NHS notes that BMI thresholds may need adjusting for some ethnic groups. South Asian, Chinese and Black African populations may face higher health risks at lower BMI levels
Use the results as a general reference point. For personalised advice, speak to your GP or a registered dietitian — especially if you are managing a health condition or planning significant weight change.
Frequently asked questions
How does the ideal weight calculator work?
Enter your height and biological sex. The calculator compares three clinical methods — the NHS BMI-based healthy weight range, the Hamwi formula and the Devine formula — to give you a personalised ideal weight estimate.
What is the NHS healthy weight range?
The NHS defines a healthy weight as a BMI between 18.5 and 24.9. The calculator multiplies your height in metres squared by these BMI boundaries to produce your healthy weight range in kilograms.
What is the Hamwi formula?
The Hamwi formula estimates ideal body weight using a base weight for the first 5 feet of height, then adds a fixed amount per additional inch. For men it starts at 48 kg plus 2.7 kg per inch; for women it starts at 45.5 kg plus 2.2 kg per inch.
What is the Devine formula?
The Devine formula was originally developed for drug dosage calculations. It uses a base of 50 kg for men or 45.5 kg for women, adding 2.3 kg for each inch of height above 5 feet. It tends to produce slightly different results to Hamwi.
Why do the three formulas give different results?
Each formula was developed for a different purpose and uses a different methodology. The NHS range is based on BMI population data, while Hamwi and Devine use height-based linear equations from clinical research. Comparing all three gives a more rounded picture.
Is ideal weight the same for everyone of the same height?
No. These formulas provide general estimates based on height and sex, but individual factors like muscle mass, bone density, body frame size and ethnicity all affect what a healthy weight looks like for you. Use the results as a starting point, not a diagnosis.