Ideal Body Weight Calculator UK, 4 Formula Comparison

Ideal Body Weight

Devine - Robinson - Miller - Hamwi

Sex

Height

Current Weight (for comparison)

Frame Size

Recommended Ideal Weight (average)

Your current weight -

Difference -

Healthy BMI range for height -

Formula 1

Devine

1974, Most widely used clinically

Originally developed for drug dosing calculations. Still the most common formula used in medical practice.

Formula 2

Robinson

1983, Refined Devine formula

A revision of Devine designed to better match observed healthy weights from large population studies.

Formula 3

Miller

1983, Tends lowest estimate

Often produces the lowest ideal weight estimate. Developed alongside Robinson in the same study.

Formula 4

Hamwi

1964, Oldest formula

The oldest of the four formulas. Used a rule-of-thumb approach and tends to produce slightly higher estimates.

Formula Comparison - Orange line = your current weight

To Lose / Gain

vs average ideal weight

Est. Weeks

at 500 kcal/day deficit

Est. Reach Date

at current pace

These formulas were designed for adults of average build and may not apply to athletes, highly muscular individuals, or people under 18. The average of all four is the most balanced estimate to use as a target.

The Guide

What Is Ideal Body Weight & Which Formula Is Most Accurate?

An ideal body weight (IBW) formula gives you a target weight based on your height and sex. These formulas were originally developed for medical use, primarily for calculating drug doses and assessing nutritional needs, rather than as aesthetic or fitness targets. Understanding what each one represents helps you use the result in context.

No single formula is universally "correct", they all have limitations and were developed on different populations. The most useful approach is to look at the average across all four and consider it alongside your BMI, body fat percentage, and how you actually feel.

The Four Formulas Explained

Formula	Year	Male Base (5'5" / 165cm)	Female Base (5'5" / 165cm)
Devine	1974	~68 kg	~58 kg
Robinson	1983	~67 kg	~57 kg
Miller	1983	~64 kg	~59 kg
Hamwi	1964	~70 kg	~60 kg

Frame Size Adjustment

Most ideal body weight formulas can be adjusted by -10% for body frame size. People with a large frame (broad shoulders, wider bone structure) can add up to 10% to the base estimate. People with a small frame can subtract up to 10%. Frame size is roughly estimated by wrapping your thumb and middle finger around your wrist, if they overlap you're small-framed, if they just touch you're medium, and if they don't meet you're large-framed.

Why Ideal Body Weight Is Just A Starting Point

These formulas don't account for muscle mass, and a muscular person may be well above their calculated IBW while being in excellent health. Conversely, someone at their IBW but with high body fat and low muscle (known as "skinny fat") may have worse health markers than someone slightly above IBW with good body composition. Use IBW as one data point among several, not as a rigid target.

A Better Way To Set Your Weight Goal

Rather than targeting a specific scale weight, consider setting a goal based on a combination of BMI (18.5-24.9), body fat percentage (6-17% for men, 14-24% for women), and waist circumference (under 94cm for men, 80cm for women). These three measures together give a much more complete picture of health than scale weight alone.

Frequently Asked Questions

No single formula is definitively most accurate, they were all developed on different populations and for different purposes. Research comparing them suggests the Devine formula performs reasonably well for most people and remains the most clinically used. However, using the average of all four gives the most balanced estimate and accounts for the variation between methods.

Not necessarily, these formulas were designed for medical calculations, not personal fitness goals. Someone who lifts weights regularly may be 10-15kg above their calculated IBW and be in excellent shape. Focus on body composition (fat vs muscle), energy levels, and health markers rather than hitting a specific number on the scale.

People with larger skeletal frames naturally weigh more at the same height. Large-framed individuals can add up to 10% to the base IBW estimate; small-framed individuals can subtract up to 10%. A rough way to determine frame size: wrap your thumb and index finger around your wrist. If they overlap = small frame. If they barely touch = medium. If there's a gap = large frame.

Not reliably. Athletes and heavily muscled individuals will almost always exceed their calculated IBW due to greater muscle mass. For athletes, body fat percentage is a far more relevant metric, a male powerlifter at 90kg and 10% body fat is in excellent shape regardless of what an IBW formula says.

At a sustainable rate of 0.5kg per week (500 kcal/day deficit), divide the amount you need to lose in kg by 0.5 to get the number of weeks. For example, losing 15kg takes approximately 30 weeks. Going faster risks muscle loss and metabolic adaptation, slower and steadier produces better long-term results.

Ideal Body Weight