Calculate your Body Mass Index (BMI) to find out whether you are a healthy weight for your height. This calculator uses the standard BMI formula and shows your BMI score, weight category and healthy weight range.
BMI is calculated by dividing your weight in kilograms by your height in metres squared: BMI = kg/m². For example, someone who weighs 75kg and is 1.75m tall has a BMI of 75 ÷ (1.75 × 1.75) = 24.5, which falls in the healthy weight range.
BMI is a useful screening tool but has limitations. It does not account for muscle mass, bone density, body fat distribution or ethnic differences. Athletes and very muscular people may have a high BMI but low body fat. Older adults may have a healthy BMI but still carry excess body fat.
BMI should be used as one of several indicators of health rather than a definitive measure. Always consult a healthcare professional for personalised advice about your weight and health.
BMI was developed in the 1830s using data from European populations and doesn't account for modern understanding of body composition. Athletes and bodybuilders often register as overweight or obese despite having very low body fat because muscle weighs more than fat — a rugby player at 95kg and 1.8m tall has a BMI of 29.3 (overweight) but may have only 12% body fat. Conversely, older adults or those who are sedentary might have a healthy BMI of 23 but carry excess visceral fat around organs while having lost muscle mass, putting them at higher health risk than their BMI suggests. Ethnic differences also matter: South Asian populations tend to carry more body fat at lower BMIs, whilst Black populations often have denser bones and more muscle mass, meaning standard BMI ranges may not apply equally. Women naturally carry more essential body fat than men (10-13% vs 2-5%) which BMI doesn't distinguish. Very tall or very short people find BMI less accurate as the formula doesn't scale perfectly across all heights. For these reasons, BMI works best as a population-level screening tool rather than an individual diagnostic measure.
If your BMI suggests you're overweight or obese, first consult your GP for a full health assessment including waist circumference, blood pressure, cholesterol levels and blood sugar tests which provide better insight into health risks than BMI alone. Many people with high BMI are metabolically healthy with no elevated health markers. If intervention is needed, focus on sustainable lifestyle changes rather than crash diets: reduce portion sizes, increase vegetable intake, limit processed foods and added sugars, and aim for 150 minutes weekly moderate activity like brisk walking. A loss of just 5-10% bodyweight significantly improves health markers even if you remain in the overweight category. For underweight BMI, rule out underlying health conditions first as unintentional weight loss can indicate thyroid problems, digestive disorders or mental health issues. If appetite is the issue, eat calorie-dense nutritious foods like nuts, avocados, full-fat dairy and nut butters. Consider strength training to build muscle mass healthily rather than just gaining fat. Small frequent meals may be easier than large ones. Both extremes benefit from registered dietitian guidance for personalised nutrition plans. Remember that healthy weight isn't just a number — energy levels, fitness, mental health and blood markers matter more than hitting a specific BMI target.
Yes, many UK insurance providers use BMI as one factor in calculating premiums, though it's not the only consideration. Life insurance underwriters typically view BMI over 30 as increased mortality risk, potentially raising premiums or requiring additional medical screening. Some insurers apply loading (additional charges) for BMI over 35, and may decline cover entirely above BMI 40-45 unless applicants demonstrate stable health with favourable blood tests and no obesity-related conditions. Critical illness insurance similarly considers BMI, with higher premiums for those outside the 19-30 range. However, insurers also assess overall health: a fit individual with BMI 32 due to muscle mass and normal blood pressure may get better rates than someone with BMI 27 but high cholesterol and diabetes. Private medical insurance premiums may increase with higher BMI due to greater likelihood of needing treatment for weight-related conditions like joint problems, sleep apnea or cardiovascular disease. Income protection insurance also factors in BMI as obesity correlates with more sick days and longer-term disability. The good news is that losing weight can lead to premium reductions at renewal if your BMI drops into a healthier range and you can demonstrate sustained lifestyle changes. If you're declined cover due to BMI, specialist brokers can sometimes find insurers with more flexible underwriting criteria, or you may qualify for guaranteed acceptance policies albeit at higher cost.
BMI = 75 ÷ (1.80 × 1.80) = 75 ÷ 3.24 = 23.1. This falls in the healthy weight range (18.5-24.9). For this height, healthy weight range is 60-81kg. This person is well within healthy limits and should maintain current weight through balanced diet and regular activity.
BMI = 82 ÷ (1.65 × 1.65) = 82 ÷ 2.72 = 30.1. This is just into the obese category (30+). For this height, healthy weight range is 50-68kg. A realistic first goal would be 75kg (BMI 27.5, overweight but significantly healthier) then reassess. Losing 7kg brings substantial health benefits without requiring perfection.
BMI = 52 ÷ (1.70 × 1.70) = 52 ÷ 2.89 = 18.0. This is just below healthy range (18.5+) and considered underweight. For this height, healthy weight range starts at 53.5kg. However, teenagers should use BMI-for-age charts rather than adult calculations as their bodies are still developing. Consult a doctor if concerned about teenage weight as growth spurts affect BMI significantly.
While BMI provides a starting point, comprehensive health assessment requires additional measurements and factors. Waist circumference is a better predictor of cardiovascular risk than BMI: men over 94cm (37 inches) and women over 80cm (31.5 inches) face increased health risks regardless of BMI, as abdominal fat is more metabolically active and dangerous than subcutaneous fat elsewhere. The waist-to-hip ratio further refines this by comparing waist to hip measurements — values above 0.90 for men or 0.85 for women indicate central obesity risk. Body fat percentage measured through bioelectrical impedance scales or DEXA scans provides actual composition data: healthy ranges are 10-20% for men and 18-28% for women, though athletes may be lower. Blood pressure, fasting glucose, cholesterol profile and inflammatory markers like C-reactive protein reveal metabolic health that BMI cannot capture — some obese individuals are metabolically healthy whilst some normal-weight people have concerning blood markers. Fitness level measured through VO2 max or simple tests like walking a mile strongly predicts longevity independent of weight: fit overweight people outlive unfit normal-weight people. Mental health and relationship with food matter enormously: someone at healthy BMI through restrictive eating and exercise addiction is less healthy than someone slightly overweight who eats intuitively and enjoys movement. Sleep quality, stress levels, social connections and life satisfaction all impact health more than a few BMI points. Finally, genetic factors influence optimal weight: some people thrive at BMI 22 while others feel and perform best at BMI 27. Focus on adding healthy behaviours (more vegetables, regular activity, good sleep) rather than obsessing over weight targets, and let your body find its natural equilibrium.