Quick answer: BMI = weight in kg ÷ (height in metres)². Below 18.5 is underweight, 18.5–24.9 healthy, 25–29.9 overweight, 30+ obese. Enter your height and weight below for your exact BMI and health category.
📝 Worked example
70 kg, 1.75 m tall → BMI = 70 ÷ (1.75 × 1.75) = 70 ÷ 3.0625 = 22.9 — healthy range (18.5–24.9).
✓ 100% FREE — No Signup Needed
Enter your height and weight for an instant body mass index, category, and healthy weight range.
Part of the Health Tools collection — browse all related free tools.
For adults, a BMI below 18.5 is underweight, 18.5–24.9 is healthy, 25–29.9 is overweight, and 30 or above is obese. It is a useful starting point, not a diagnosis.
BMI is a ratio, not a plan — your BMR tells you what you burn and the calorie calculator turns it into a daily target.
BMI compares weight with height. It does not directly measure body fat, muscle, bone density, or overall health.
For a woman over 50, the standard healthy BMI range is 18.5–24.9, though many doctors consider 25–27 acceptable for older adults because muscle loss with age can distort the number. Use this free BMI calculator for your number, then review it with your doctor alongside other health measures.
Good question — and a common one: how accurate is BMI for women over 50? It is a useful first screen but a weak final verdict. After 50, sarcopenia (age-related muscle loss of roughly 3–8% per decade) means two women with the same BMI can carry very different amounts of body fat, and postmenopausal hormonal shifts move fat toward the belly even when weight barely changes — the “normal-weight obesity” problem. BMI also misses bone-density loss, so pair your number with a waist measurement (above 88 cm / 35 in signals higher health risk regardless of BMI), activity level and, if you want precision, a body-composition check such as DEXA or bioelectrical impedance (BIA). Always review the result with your doctor alongside blood pressure, cholesterol and strength.
BMI stands for body mass index. It is a screening measure that compares an adult's weight with the square of their height.
For most adults, the standard healthy range is 18.5 to 24.9. Individual health varies, so interpret the result alongside other health information.
BMI may overestimate body fat in muscular athletes. Children and teens require age- and sex-specific BMI percentiles, so this adult calculator is not suitable for them.
The calculator shows the weight range corresponding to a BMI of 18.5–24.9 for your height. “Ideal” weight is personal and may differ based on health, body composition, and medical advice.
Once a month is plenty for most people. Weight changes slowly, and checking too often can be discouraging because of normal daily fluctuations from water and food.
BMI can mislead for very muscular people, because muscle weighs more than fat. It also works less well for children, pregnant women, and older adults. Treat it as a starting point, not a final verdict.
Yes — this free online BMI calculator for women with age is built for exactly that: enter your height and weight, in metric or imperial units, and get your BMI, your weight category, and the healthy weight range for your height. It adds age-aware guidance for women over 50, since muscle loss with age can shift what the number means. Everything runs in your browser — free, no signup.
Metric BMI is your weight in kilograms divided by your height in metres squared. Imperial BMI is your weight in pounds multiplied by 703, divided by your height in inches squared. The calculator above does the math for you in either system.
For a woman at 60, a practical ideal-weight range is the weight matching a BMI of 22–27 for her height — roughly 49–65 kg at 163 cm (5'4") and 55–73 kg at 170 cm (5'7"). Classic formulas agree closely: the Devine formula gives about 53 kg for 163 cm, Robinson about 53 kg, Miller about 55 kg. After 60, doctors often accept the upper end of the range, because a little reserve weight protects against frailty and bone loss. The calculator above shows the healthy range for your exact height in kg or lb.
For most adults, the standard healthy BMI range is 18.5 to 24.9. BMI is a screening tool and does not diagnose health — your doctor interprets it alongside other health measures.
Not always. BMI does not directly measure body fat and may be less informative for athletes, pregnant people, older adults, or children. A healthcare professional can interpret your number in context.
For adults 18 and over. This calculator provides general information and is not medical advice.
Body Mass Index (BMI) is a simple number calculated from your height and weight that gives a quick picture of whether your weight sits in a healthy range. It was developed in the 1830s by the Belgian mathematician Adolphe Quetelet and is still used worldwide by doctors, fitness professionals, and health organisations as a first screening step.
BMI does not measure body fat directly. Instead, it estimates whether your weight is proportionate to your height, which is why it needs only two numbers and takes less than a minute. Millions of people check their BMI every month before starting a diet, joining a gym, or visiting a doctor, because it turns two measurements into one easy-to-understand result with a clear category: underweight, healthy, overweight, or obese.
For women over 50, a BMI calculator needs context: muscle mass naturally declines with age, so BMI can read slightly higher even as body fat stays the same. Many doctors consider a BMI of 25–27 acceptable for older adults, while a very low BMI can signal frailty. This free calculator works for any adult — enter your height and weight for your BMI, category and the healthy weight range for your height, then discuss the result with your doctor alongside blood pressure, cholesterol and activity level.
Worked example: 65 kg at 1.65 m → BMI = 65 ÷ 1.65² ≈ 23.9, in the healthy range.
“Ideal weight” formulas (Devine 1974, Robinson, Miller, Hamwi) were designed from height and a medium frame: a 60-year-old woman at 163 cm (5'4") gets roughly 53–55 kg across all four formulas, and at 170 cm (5'7") roughly 60–63 kg. In practice, geriatric guidance prefers a BMI band of 23–28 for the 55–64 band and 24–29 for 65+, so the table below shows healthy kg ranges rather than a single number — small frames take the lower end, larger frames the upper end.
For a frame-by-frame breakdown, try our free ideal weight calculator, which covers small, medium and large frames in kg and lb.
This BMI calculator works the same way for women over 60 — but the number needs senior context. Research (including a 2014 JAMA meta-analysis) finds a BMI of roughly 23–30 in older adults carries no higher mortality risk than the standard 18.5–24.9 — the so-called “obesity paradox,” driven by the protective effect of reserve weight against frailty, falls and malnutrition. For Asian and South Asian women, cutoffs run lower: overweight starts at 23 and obesity at 27.5, with a healthy ceiling near 23.
Frame-size guidance (women, height in cm): small frame 150–157 cm → 44–54 kg; medium frame 150–157 cm → 48–58 kg; large frame 150–157 cm → 52–64 kg. At 160–167 cm: small 50–59 kg, medium 54–65 kg, large 58–71 kg. At 168–175 cm: small 55–65 kg, medium 60–71 kg, large 64–78 kg. These are screening bands, not diagnoses.
Worked example: 62 kg at 1.60 m → BMI = 62 ÷ 1.60² ≈ 24.2 — healthy by the standard scale and well inside the senior-optimal band. Enter your own height and weight above for your exact result, then track muscle and waist size alongside the number.
BMI (body mass index) is weight divided by height squared: BMI = weight(kg) ÷ height(m)². Worked example: a person weighing 80 kg at 1.80 m tall — 80 ÷ (1.80 × 1.80) = 80 ÷ 3.24 = 24.7, inside the healthy range.
Under 18.5 — underweight · 18.5–24.9 — healthy weight · 25–29.9 — overweight · 30 and above — obese. These cut-offs come from the World Health Organization and are used by health systems worldwide as a first screening step.
BMI cannot tell muscle from fat. A rugby player at 95 kg and 1.85 m scores 27.8 ("overweight") while carrying very little body fat — for muscular people, waist circumference (under 94 cm for men, 80 cm for women per WHO) or body-fat percentage is a better guide. BMI also underestimates risk in older adults, who lose muscle with age, and it is not calibrated for pregnancy or children (who use age-based percentile charts instead).
Use the calculator above as a starting point: if your BMI is 25 or above and your waist measurement is high, that combination is the signal worth acting on — ideally with a clinician's input.