Calculate your Body Mass Index (BMI) using our verified BMI Calculator NHS tool. Discover whether your weight is currently in a healthy range, view tailored recommendations based on UK health standards, and check your personalised healthy weight target for your height.
Body Mass Index (BMI) is a clinical screening metric utilised by general practitioners and public health services across the United Kingdom. Whether measuring in stones and pounds or kilograms and centimetres, our calculator provides immediate, actionable feedback alongside adjusted NICE thresholds for diverse ethnic backgrounds.
For most UK adults, a healthy BMI is 18.5 to 24.9 kg/m². People of South Asian, Black African, African-Caribbean, and Middle Eastern ancestry face elevated metabolic risks starting at 23.0 kg/m².
Enter your measurements below for an instant NHS-aligned assessment.
The NHS uses internationally standardised thresholds defined by the World Health Organization (WHO) and refined by the National Institute for Health and Care Excellence (NHS BMI Chart guidelines) to screen for healthy weight in adults.
Body Mass Index (BMI) is an objective mathematical index relating body mass to stature. In the UK healthcare system, general practitioners, practice nurses, health visitors, and dietitians use BMI as the primary initial screening tool to evaluate population health, diagnose nutritional deficiencies, and identify early risk factors for chronic metabolic and cardiovascular disease.
Being underweight may indicate insufficient calorie intake, nutritional malabsorption, or underlying health conditions. Clinical risks include immune system compromise, muscle wasting, anaemia, hormonal irregularities, and bone density loss (osteoporosis).
NHS Advice: Consult your GP or an NHS registered dietitian to explore nutrient-dense, calorie-rich dietary strategies for healthy, steady weight gain.
This category represents the statistical optimum where risks of cardiovascular illness, stroke, Type 2 diabetes, and weight-associated cancers are lowest. Physiological systems operate with minimal strain on the heart, joints, and metabolic organs.
NHS Advice: Maintain your balance through a wholesome Mediterranean-style diet, adequate hydration, and at least 150 minutes of weekly moderate aerobic activity.
Carrying excess body weight places cumulative strain on joints, blood vessels, and endocrine organs. Early lifestyle adjustments can successfully reverse weight progression before clinical obesity develops.
NHS Advice: Explore our Calorie Deficit Calculator NHS to structure a sustainable 500 kcal daily deficit targeting 0.5–1 kg weekly weight loss.
Subdivided into Class I (30.0–34.9), Class II (35.0–39.9), and Class III (40.0+ / severe obesity). Obesity is recognised by the NHS as a complex, chronic condition requiring supportive clinical management to prevent secondary complications.
NHS Advice: Speak with your GP practice to access local NHS Tier 2 community lifestyle programmes or Tier 3 specialist multidisciplinary clinics.
Under NICE clinical guidelines (PH46 and CG189), adults from South Asian (Indian, Pakistani, Bangladeshi), Black African, African-Caribbean, Chinese, and Middle Eastern ancestries tend to store higher proportions of visceral (abdominal) body fat at lower total body weights. Consequently, metabolic and cardiovascular risks climb at lower thresholds:
Our calculator above automatically applies these NICE-recommended thresholds when you choose your ethnic background in the selector.
Accurate inputs are essential for a reliable BMI score. Follow these clinical measuring protocols recommended by NHS health visitors and practice nurses.
Compare your height against standard weight brackets to quickly locate your BMI classification. For detailed breakdowns by gender and age, explore the complete NHS BMI Chart reference.
| Height (Imperial) | Height (Metric) | Underweight (<18.5) | Healthy Range (18.5–24.9) | Overweight (25–29.9) | Obese (30.0+) |
|---|---|---|---|---|---|
| 5 ft 0 in | 152 cm | Under 6 st 9 lb (<42.8 kg) | 6 st 9 lb – 9 st 2 lb (42.8 – 57.6 kg) | 9 st 3 lb – 10 st 13 lb (57.7 – 69.1 kg) | 11 st 0 lb+ (69.2 kg+) |
| 5 ft 2 in | 157 cm | Under 7 st 2 lb (<45.6 kg) | 7 st 2 lb – 9 st 9 lb (45.6 – 61.4 kg) | 9 st 10 lb – 11 st 9 lb (61.5 – 73.7 kg) | 11 st 10 lb+ (73.8 kg+) |
| 5 ft 4 in | 163 cm | Under 7 st 10 lb (<49.2 kg) | 7 st 10 lb – 10 st 5 lb (49.2 – 66.2 kg) | 10 st 6 lb – 12 st 7 lb (66.3 – 79.4 kg) | 12 st 8 lb+ (79.5 kg+) |
| 5 ft 6 in | 168 cm | Under 8 st 3 lb (<52.2 kg) | 8 st 3 lb – 11 st 1 lb (52.2 – 70.3 kg) | 11 st 2 lb – 13 st 4 lb (70.4 – 84.4 kg) | 13 st 5 lb+ (84.5 kg+) |
| 5 ft 8 in | 173 cm | Under 8 st 12 lb (<55.4 kg) | 8 st 12 lb – 11 st 12 lb (55.4 – 74.6 kg) | 11 st 13 lb – 14 st 3 lb (74.7 – 89.5 kg) | 14 st 4 lb+ (89.6 kg+) |
| 5 ft 10 in | 178 cm | Under 9 st 4 lb (<58.6 kg) | 9 st 4 lb – 12 st 8 lb (58.6 – 78.9 kg) | 12 st 9 lb – 15 st 2 lb (79.0 – 94.7 kg) | 15 st 3 lb+ (94.8 kg+) |
| 6 ft 0 in | 183 cm | Under 9 st 13 lb (<62.0 kg) | 9 st 13 lb – 13 st 5 lb (62.0 – 83.4 kg) | 13 st 6 lb – 16 st 1 lb (83.5 – 100.1 kg) | 16 st 2 lb+ (100.2 kg+) |
| 6 ft 2 in | 188 cm | Under 10 st 5 lb (<65.4 kg) | 10 st 5 lb – 14 st 1 lb (65.4 – 88.0 kg) | 14 st 2 lb – 17 st 0 lb (88.1 – 105.7 kg) | 17 st 1 lb+ (105.8 kg+) |
Looking for a specific height breakdown? View our dedicated guide on Healthy Weight Range by Height and Ideal Weight by Height UK formulas.
A common misconception is that there is one exact "ideal weight" for every individual. In clinical practice, the NHS and medical professionals recognise that body frame size, bone structure, and muscle composition vary significantly.
Rather than prescribing a single number, clinicians calculate a healthy weight window corresponding to a BMI between 18.5 and 24.9. Within this span, physiological systems function efficiently without excessive cardiac or metabolic strain.
To learn more about traditional formulas such as the Devine, Robinson, and Miller equations compared to modern BMI midpoints, check our Ideal Weight by Height UK resource.
NICE guidelines strongly recommend measuring your waist circumference alongside BMI. Excess fat stored centrally around the abdominal cavity (visceral fat) is metabolically active and releases inflammatory chemicals into the bloodstream.
The Golden Rule: Keep your waist circumference to less than half your height (a waist-to-height ratio below 0.5).
Two individuals with the exact same BMI can look completely different depending on their lean muscle proportion and fat distribution. Explore our Visual BMI Calculator to see 3D representations of various body types.
To measure your waist correctly, find the midpoint between the bottom of your ribs and the top of your hips (usually level with the belly button), breathe out naturally, and wrap a tape measure flat against your skin.
| Waist-to-Height Ratio | Risk Classification | Clinical Significance | Recommended NHS Action |
|---|---|---|---|
| Less than 0.40 | Underweight / Low | Potential indicator of low calorie intake or muscle depletion. | Review nutritional balance with a GP or dietitian. |
| 0.40 to 0.49 | Healthy (No Increased Risk) | Optimal visceral fat levels; lowest cardiovascular and metabolic risk. | Maintain active lifestyle and balanced diet. |
| 0.50 to 0.59 | Increased Health Risk | Elevated visceral adiposity around liver, kidneys, and pancreas. | Incorporate daily physical activity and a moderate calorie deficit. |
| 0.60 or Greater | High / Very High Risk | Significantly heightened probability of Type 2 diabetes and hypertension. | Consult GP for metabolic assessment and NHS weight management options. |
If your BMI calculation indicates that you are in the overweight or obese category, the NHS provides structured, multi-tiered support pathways depending on your health profile.
Calculate your personal target intake with our Calorie Deficit Calculator NHS.
Important: Adult BMI formulas should never be applied directly to children and adolescents aged 2 to 18.
Because children are growing rapidly and body composition changes throughout puberty, healthcare professionals use BMI Centiles (Percentiles) based on UK-WHO growth references.
A child's BMI is plotted against thousands of peers of the same age and biological sex to determine whether they are on an expected growth trajectory.
Use our dedicated Child Growth Chart Calculator UK and Percentile Calculator UK for younger family members.
The NHS operates a 4-tier model of weight management services across England, Scotland, Wales, and Northern Ireland:
Self-directed public health interventions including the NHS Digital Weight Loss Plan, Better Health campaigns, Couch to 5K, and Eatwell Guide resources.
12-week multi-component lifestyle, dietary, and exercise programmes funded through local councils and GP surgeries (e.g. Slimming World, WW, or local group programmes).
Clinics led by specialist hospital physicians, bariatric dietitians, and clinical psychologists. Evaluates weight loss pharmacotherapy (e.g. GLP-1 medications like Wegovy) under NICE guidance.
Specialist surgical interventions (gastric bypass, sleeve gastrectomy) for adults with BMI ≥ 40 kg/m², or BMI ≥ 35 kg/m² with significant comorbidities who completed Tier 3.
Epidemiological research conducted by the British Heart Foundation, Cancer Research UK, and NHS England demonstrates clear correlations between elevated BMI and several systemic conditions.
Excess mass increases peripheral arterial resistance, forcing the left ventricle to pump with greater force. This accelerates arterial atherosclerosis, raising risks of myocardial infarction (heart attack) and ischaemic stroke.
Adipose tissue—especially intra-abdominal visceral fat—releases free fatty acids and inflammatory cytokines (e.g. TNF-alpha, IL-6) that cause insulin receptor resistance in muscle and liver cells.
Every extra kilogram of body weight exerts roughly 4 kg of pressure on the knee joints during walking. Over time, this accelerates cartilage wear, leading to chronic knee, hip, and lower spine osteoarthritis.
Increased soft tissue in the pharyngeal area can collapse during sleep, causing episodic breathing cessation (apnoea), nocturnal hypoxia, chronic daytime fatigue, and pulmonary hypertension.
In geriatric medicine, clinical evidence suggests that an adult aged 65 or older may benefit from a slightly higher BMI (approximately 23.0 to 27.9 kg/m²). A modest nutritional reserve provides vital protection against age-related muscle loss (sarcopenia), falls, bone fractures, and recovery from acute illnesses.
Body weight is only one component of your overall health profile. Staying properly hydrated and monitoring cardiovascular indicators are vital steps in disease prevention.
The NHS Eatwell Guide recommends drinking 6 to 8 cups or glasses of fluid daily (approx. 1.5 to 2.5 litres), which includes water, lower-fat milk, sugar-free drinks, and tea or coffee. Proper hydration supports metabolic efficiency, kidney function, and energy levels.
Estimate your personal hydration requirement based on weight, climate, and exercise level with the Water Intake Calculator NHS.
Carrying excess body weight significantly increases the workload on your heart, raising systolic and diastolic blood pressure. Over time, hypertension damages arterial walls and accelerates cardiovascular risk.
Review your numbers against UK clinical thresholds using our Blood Pressure Chart UK and estimate your 10-year cardiovascular risk profile with the QRISK Calculator NHS.
Body Mass Index was developed in the 19th century by Belgian mathematician Adolphe Quetelet and remains the international standard for population-level weight screening.
Example: For an adult weighing 72 kg with a height of 1.75 m:
Example: For someone weighing 11 stone 4 lbs (158 lbs) at 5 ft 9 in (69 inches):
While BMI is an effective initial screening tool for the vast majority of the population, it is not a direct measure of body fat percentage. It does not distinguish between skeletal muscle mass and adipose tissue. Muscular athletes, pregnant women, and elderly individuals experiencing sarcopenia (muscle loss) may receive skewed results.
Our online tools and health documentation are built strictly upon evidence-based, peer-reviewed clinical guidelines published by recognised UK and international health authorities.
bmicalculatornhs.net is an independent digital health calculator designed strictly for informational and educational screening purposes. It is not an official service of NHS England or the Department of Health and Social Care, nor does it provide formal medical diagnosis, treatment, or personalised clinical advice.
Always consult a qualified General Practitioner (GP), registered dietitian, or health professional before undertaking significant changes to your diet, exercise regime, or weight management plan.
Common questions regarding NHS BMI calculations, healthy weight ranges, and UK health guidance.
Body Mass Index (BMI) is an established clinical screening metric that uses your height and weight to estimate whether you are carrying a healthy amount of body fat. NHS clinical guidelines define an adult healthy BMI as falling between 18.5 and 24.9 kg/m².
For adults of White European heritage:
NICE (National Institute for Health and Care Excellence) guidelines highlight that individuals from South Asian, Black African, African-Caribbean, Chinese, and Middle Eastern ancestry tend to accumulate higher percentages of visceral body fat at lower BMIs. To account for this increased metabolic and cardiovascular risk, NICE recommends an "increased risk" trigger at 23.0 kg/m² and "high risk" trigger at 27.5 kg/m².
Yes. BMI is based solely on total body mass relative to height. Dense lean muscle tissue weighs more by volume than fat. Bodybuilders, rugby players, and athletic individuals may have a high BMI despite having low body fat percentages. For these individuals, waist circumference and body fat scans provide more meaningful insight.
There are 14 pounds in 1 stone, and 1 pound equals approximately 0.453592 kg (1 stone ≈ 6.35029 kg). To convert, multiply your stones by 14, add remaining pounds, and multiply the total by 0.453592. Our calculator computes this automatically when you select the Imperial mode.
Children and adolescents are experiencing rapid bone and muscle growth. Fixed adult cut-offs cannot accurately reflect healthy pediatric development. Instead, the NHS uses BMI Centiles (Percentiles) based on UK-WHO growth charts. Please visit our Child Growth Chart Calculator UK to calculate centiles for young people aged 2–18.
NICE recommends keeping your waist measurement to less than half your height. For example, if you are 5 ft 8 in (68 inches / 173 cm) tall, your waist should ideally be less than 34 inches (86 cm). This measurement specifically assesses central adiposity, which is a strong predictor of cardiovascular disease and Type 2 diabetes.
Under NICE Technology Appraisals (TA875 / TA902), GLP-1 receptor agonists (such as semaglutide / Wegovy and tirzepatide / Mounjaro) can be prescribed on the NHS within specialist Tier 3 weight management services for adults with:
Consult your GP to discuss clinical eligibility and local NHS service availability.
For individuals with a stable, healthy BMI, checking your weight and waist circumference once every 3 to 6 months is generally sufficient. If you are actively participating in an NHS weight management programme or calorie deficit plan, weighing yourself once weekly (on the same morning, under identical conditions) provides the most reliable progress trend without daily fluid retention noise.
Clothing waistbands usually sit lower down on the hips or pelvic bone, and clothing manufacturers often use "vanity sizing". In contrast, clinical waist circumference is measured precisely at the midpoint between the bottom of your lowest rib and the top of your pelvic hip bone (iliac crest), roughly level with your navel. This clinical measurement is usually 2 to 4 inches larger than your high-street trouser tag.
No. Standard adult BMI calculation is not valid during pregnancy due to the physiological weight of the growing fetus, placenta, amniotic fluid, expanded blood volume, and maternal breast tissue. NHS midwives assess pre-pregnancy BMI at the initial booking appointment (around 8–10 weeks) to guide maternal care pathways. Postpartum women should allow adequate recovery and consult their GP or health visitor before initiating calorie-restrictive weight management.
The NHS Health Check is a preventative screening programme offered every 5 years to UK residents aged 40 to 74 without pre-existing cardiovascular conditions. It includes an assessment of your BMI, waist circumference, blood pressure, cholesterol levels, and blood sugar (HbA1c) alongside an estimated 10-year QRISK cardiovascular score to help prevent stroke, heart attacks, kidney disease, and Type 2 diabetes.