Ideal Weight Calculator UK – Calculate Your Target Body Weight
Use our evidence-aligned Ideal Weight Calculator UK to determine your optimal body weight based on your biological sex, height, and skeletal frame size. Compare the NHS healthy weight range (BMI 18.5–24.9 kg/m²) alongside four classic medical equations (Devine, Robinson, Miller, and Hamwi) to establish a realistic, clinically grounded health target.
NHS Healthy Weight Range:
8 st 10 lb – 11 st 10 lb (55.4 – 74.5 kg)
Medical & Clinical Formula Breakdown
- Devine (1974 - Hospital Standard) 10 st 11 lb (68.4 kg)
- Robinson (1983 - Metropolitan Life) 10 st 7 lb (66.8 kg)
- Miller (1983 - Refined Linear) 10 st 5 lb (65.6 kg)
- Hamwi (1964 - Clinical Dietetics) 10 st 13 lb (70.0 kg)
How This UK Ideal Weight Calculator Computes Your Target
Unlike simple charts that provide a single arbitrary number, our ideal weight calculator synthesises two distinct scientific methodologies: modern NHS epidemiological healthy BMI ranges and validated clinical Ideal Body Weight (IBW) equations used in UK pharmacokinetics and dietetics.
1. NHS Population Midpoint
The NHS defines healthy weight for adults as a Body Mass Index between 18.5 and 24.9 kg/m². The optimal statistical midpoint corresponds to a BMI of 22.0 for men and 21.7 for women, where epidemiological data shows the lowest all-cause mortality and cardiovascular risks.
Target: Height (m)² × 22.0 (Men) / 21.7 (Women)
2. Clinical Linear Formulas
Equations like Devine, Robinson, and Hamwi assign a baseline weight for an adult standing 5 feet tall (60 inches) and add incremental weight per additional inch. These formulas are widely used across the NHS to calculate renal clearances and therapeutic drug dosages.
Accounts for gender-specific physiological differences.
3. Skeletal Frame Adjustments
Bone mass contributes approximately 12% to 15% of total body mass. Our tool allows you to adjust baseline estimates by ±10% depending on whether you have a light, medium, or heavy bone structure (determined via wrist circumference).
Prevents penalising naturally heavy skeletal frames.
To explore exact lower and upper boundaries for all heights in stones, pounds, and kilograms, visit our comprehensive Healthy Weight Range by Height chart, or consult our clinical explainer on Ideal Weight by Height UK.
Mathematical Comparison of Ideal Body Weight (IBW) Formulas
Over the past six decades, clinical researchers have developed various linear models to estimate ideal body weight for medical drug administration, anaesthesia, and nutritional support. Here is how each major formula is constructed:
| Formula Name | Year & Origin | Male Formula (Over 5 Feet) | Female Formula (Over 5 Feet) | Primary Clinical Application |
|---|---|---|---|---|
| Devine Formula | 1974 (Dr. B.J. Devine) | 50.0 kg + 2.3 kg per inch > 5ft | 45.5 kg + 2.3 kg per inch > 5ft | Hospital drug dosing (aminoglycosides, theophylline) |
| Robinson Formula | 1983 (Dr. J.D. Robinson) | 52.0 kg + 1.9 kg per inch > 5ft | 49.0 kg + 1.7 kg per inch > 5ft | Empirical revision of Metropolitan Life insurance tables |
| Miller Formula | 1983 (Dr. D.R. Miller) | 56.2 kg + 1.41 kg per inch > 5ft | 53.1 kg + 1.36 kg per inch > 5ft | Weight targets for shorter individuals and light frames |
| Hamwi Formula | 1964 (Dr. G.J. Hamwi) | 48.0 kg + 2.7 kg per inch > 5ft | 45.5 kg + 2.2 kg per inch > 5ft | Rapid clinical dietetics and diabetic meal planning |
Why NHS Primary Care Emphasises a Weight Range
While clinical formulas output a single number, the NHS promotes a healthy weight range because real human bodies vary significantly in muscle density, limb proportions, and fat distribution. A healthy adult standing 5ft 8in (173 cm) can weigh anywhere from 8st 10lb (55.4 kg) to 11st 10lb (74.5 kg) while maintaining optimal cardiovascular and metabolic biomarkers.
Key Factors That Influence Your Personal Ideal Weight
A generic calculator can only calculate averages based on height and sex. To determine where within the healthy range you should ideally aim, consider three essential clinical modifiers:
1. Skeletal Frame Size (Wrist Measurement)
Two individuals of identical height and sex can have drastically different bone widths. A small-framed person carrying the same scale weight as a large-framed person may possess a significantly higher body fat percentage. You can assess your skeletal frame size using the simple wrist circumference test:
| Biological Sex | Height Bracket | Small Frame (< 10%) | Medium Frame (Standard) | Large Frame (> 10%) |
|---|---|---|---|---|
| Women | Under 5 ft 2 in (157 cm) | Wrist < 5.5 inches (14.0 cm) | Wrist 5.5 to 5.75 inches (14.0–14.6 cm) | Wrist > 5.75 inches (14.6 cm) |
| Women | 5 ft 2 in to 5 ft 5 in (157–165 cm) | Wrist < 6.0 inches (15.2 cm) | Wrist 6.0 to 6.25 inches (15.2–15.9 cm) | Wrist > 6.25 inches (15.9 cm) |
| Women | Over 5 ft 5 in (165 cm) | Wrist < 6.25 inches (15.9 cm) | Wrist 6.25 to 6.5 inches (15.9–16.5 cm) | Wrist > 6.5 inches (16.5 cm) |
| Men | Over 5 ft 5 in (165 cm) | Wrist 5.5 to 6.5 inches (14.0–16.5 cm) | Wrist 6.5 to 7.5 inches (16.5–19.0 cm) | Wrist > 7.5 inches (19.0 cm) |
2. Age and the "Geriatric Obesity Paradox"
As we age past 65, the body naturally experiences sarcopenia (gradual loss of skeletal muscle mass) and reductions in bone mineral density. Extensive epidemiological research published in the American Journal of Clinical Nutrition indicates that older adults (aged 65+) who maintain a slightly higher BMI of 23.0 to 27.0 kg/m² have lower mortality rates and greater resilience against infections, surgical recovery, and hip fractures compared to those who remain near the lower BMI boundary (18.5 to 20.0).
3. NICE Ethnic-Specific Risk Thresholds
Under NICE Guideline PH46, standard BMI cut-offs do not adequately reflect health risks for individuals of South Asian, Black African, African-Caribbean, and Chinese descent. Due to a tendency to accumulate visceral adipose tissue around abdominal organs at lower overall body weights, the recommended upper threshold for healthy weight is reduced from BMI 24.9 to 22.9 kg/m².
For complete information on ethnic threshold adjustments, read our dedicated NHS Healthy BMI Range clinical guide.
Why Weight Alone Does Not Tell the Complete Health Story
Stepping on a bathroom scale only tells you total mass—it cannot differentiate between muscle, visceral fat, subcutaneous fat, and water retention. In UK clinical practice, the NHS recommends pairing your ideal weight calculation with two crucial complementary metrics:
1. Waist-to-Height Ratio (WHtR)
NICE guideline CG189 advises all UK adults to keep their waist circumference to less than half their height (a ratio under 0.5). For example, a 5ft 8in (68 inch) adult should maintain a waist measurement under 34 inches.
✓ The best simple predictor of central visceral fat.
2. Lean Muscle Mass vs Body Fat
Athletes, rugby players, and resistance-trained individuals with high muscularity will often register as "overweight" or "obese" on standard ideal weight charts, despite having healthy body fat percentages (8–15% for men, 16–23% for women).
✓ Muscle tissue is ~18% denser than adipose tissue.
3. Metabolic Health Biomarkers
Even if your scale weight sits slightly above the mathematical ideal, your metabolic health can be exceptional if your blood pressure (< 120/80 mmHg), fasting blood glucose (< 5.5 mmol/L), and lipid profiles (HDL/triglycerides) remain optimal.
✓ Blood metrics reflect actual cardiovascular function.
Clinical Guidance on Weight Management Goals
If your current weight is currently above your calculated ideal weight, avoid extreme or crash diets. The NHS recommends aiming for a sustainable, gradual weight reduction of 0.5 kg to 1 kg (1 to 2 lbs) per week through a modest 500-calorie daily deficit and 150 minutes of moderate-intensity physical activity. A loss of just 5% to 10% of your starting weight produces profound reductions in blood pressure and diabetes risk.
Frequently Asked Questions About Ideal Weight in the UK
Find evidence-based answers to the most common questions regarding ideal body weight calculations, healthy targets, and medical formulas:
This calculator determines your ideal body weight by evaluating your biological sex, height, and skeletal frame size across two frameworks: the NHS recommended healthy BMI midpoint (BMI 21.7–22.0 kg/m²) and validated medical equations including the Devine (1974), Robinson (1983), Miller (1983), and Hamwi (1964) formulas.
An "ideal weight" formula calculates a single mathematical estimate based on average population data. In contrast, the NHS recommends a "healthy weight range" (BMI 18.5 to 24.9 kg/m²), which spans approximately 2 to 3 stones (13 to 20 kg) to accommodate natural individual differences in bone density, muscle mass, and body composition.
For clinical drug dosing, the Devine formula remains the global medical standard. However, for everyday health and lifestyle planning, the NHS BMI midpoint (BMI 22.0 for men, 21.7 for women) and the Robinson formula are widely regarded as the most realistic for modern UK populations.
While NHS BMI categories are standardised for adults aged 18 to 65, clinical research shows that adults over 65 benefit from maintaining a slightly higher BMI (23.0 to 27.0 kg/m²) to protect against sarcopenia, osteoporosis, and involuntary nutritional decline.
Wrap the thumb and index finger of one hand around the narrowest part of your opposite wrist. If your thumb and finger overlap, you have a small frame (-10% adjustment). If they touch exactly, you have a medium frame. If they do not touch, you have a large frame (+10% adjustment).
Medical Disclaimer & Usage Guidance
Educational Screening Tool: The calculations, formula comparisons, and health weight estimations provided on this page are intended solely for educational, lifestyle planning, and informational purposes. They do not constitute personalized medical advice, formal clinical diagnosis, or a prescriptive treatment plan.
Ideal weight equations are population approximations and do not directly measure visceral fat, muscle mass, or metabolic risk factors. If you are pregnant, managing an eating disorder, recovering from illness, or planning substantial dietary or exercise changes, consult a registered General Practitioner (GP) or qualified NHS dietitian.
Note on NHS Reference: This website provides tools based on publicly available UK NHS and NICE clinical guidance. It is an independent digital health resource and is not operated, endorsed, or partnered with NHS England.