2026-05-24 · bmi, calculator, weight loss, healthy weight
Updated 2026-08-19
Written by Maya Patel
Maya Patel is a WeightFAQ staff writer covering sustainable weight loss through mindful eating, flexible routines, and evidence-based nutrition. She translates research on protein, fiber, portion control, and calorie awareness into practical meal-planning guidance readers can actually follow at home. Her articles favor honest expectations over fad promises — small changes that compound, calorie bands scaled to real households, and grocery lists built around whole foods with room for real life. Maya writes for people juggling family meals, busy weeks, and long-term goals, not gym-optimized single adults with unlimited prep time.
22 min read
Medically reviewed on Aug 2, 2026
BMI Calculator (Metric & Imperial): Weight Category and Healthy Weight Range by Height
Enter your height and weight below and see your BMI, your WHO weight category, and the exact healthy-weight range for your height — in metric, imperial, or stones.
The calculator below also carries the lower Asian and South-Asian cutoffs recommended by the 2004 WHO Expert Consultation (overweight from 23, obesity from 27.5), a BMI-for-age note for teens under 20, and stones-and-pounds support for UK readers — with no sign-up and no email wall.
Adult BMI screening tool
BMI calculator
Enter your height and weight to get your BMI, WHO category, and healthy-weight range. Choose the unit system you actually use — only the relevant fields are shown.
Categories follow the WHO classification for adults aged 20 and over. BMI is a screening tool, not a diagnosis; it does not directly measure body fat or account for muscle mass, age-related muscle loss, pregnancy, or ethnicity-specific risk.
Quick reference: 1 stone = 14 pounds (about 6.35 kg). So 12 st 4 lb is 172 lb (about 78 kg), and 14 st 0 lb is exactly 196 lb (about 89 kg).
Quick stats
- BMI cutoffs (WHO): below 18.5 underweight · 18.5–24.9 healthy · 25.0–29.9 overweight · 30 and above obese.
- Obesity classes: 30.0–34.9 = Class I · 35.0–39.9 = Class II · 40.0 and above = Class III (severe).
- Asian-American BMI guidance (ADA / WHO Asian populations consultation): 23.0–27.4 overweight · 27.5 and above obese — used because cardiometabolic risk rises at lower BMIs in many South, East, and Southeast Asian populations.
Looking for more tools? See all four free weight-loss calculators in one place.
A note for UK readers (stones and pounds)
UK readers usually weigh themselves in stones and pounds rather than straight pounds or kilograms. The calculator above accepts stones directly — switch the unit toggle to “Stones & pounds” and enter your weight as, for example, 12 st 4 lb. The healthy-weight range is then shown in stones too, so you do not need to convert anything by hand.
BMI categories (WHO classification)
The World Health Organization and the U.S. National Heart, Lung, and Blood Institute use the same cut-off points to sort adult BMI into categories. This is the scale the calculator above uses.
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Normal (healthy) weight |
| 25.0 – 29.9 | Overweight |
| 30.0 – 34.9 | Obesity (class I) |
| 35.0 – 39.9 | Obesity (class II) |
| 40.0 and above | Obesity (class III, severe) |
These categories apply to most adults aged 20 and over. They are not used the same way for children and teenagers (who are assessed with age- and sex-specific percentile charts), and the thresholds may shift for some populations — see the limitations section below.
How BMI is calculated
The formula is simple:
BMI = weight (kg) ÷ height (m)²
If you think in pounds and inches, the imperial version is:
BMI = [weight (lb) ÷ height (in)²] × 703
For example, someone who weighs 75 kg and is 1.68 m tall has a BMI of 75 ÷ (1.68 × 1.68) = 75 ÷ 2.82 ≈ 26.6, which falls in the overweight range. The calculator above does this conversion for you in either unit system, so you do not need to do the math by hand.
Healthy weight by height (BMI 18.5–24.9)
Because the healthy BMI band is 18.5 to 24.9, you can translate it into an actual weight range for any height. The lookup table below covers every inch from 4’10” to 6’4” so you can find your range without doing the math. The calculator above will return the same range automatically once you enter your exact height.
| Height | Healthy weight (lb) | Healthy weight (kg) |
|---|---|---|
| 4’10” (147 cm) | 89 – 119 lb | 40 – 54 kg |
| 4’11” (150 cm) | 92 – 123 lb | 42 – 56 kg |
| 5’0” (152 cm) | 95 – 128 lb | 43 – 58 kg |
| 5’1” (155 cm) | 98 – 132 lb | 44 – 60 kg |
| 5’2” (157 cm) | 101 – 136 lb | 46 – 62 kg |
| 5’3” (160 cm) | 104 – 141 lb | 47 – 64 kg |
| 5’4” (163 cm) | 108 – 145 lb | 49 – 66 kg |
| 5’5” (165 cm) | 111 – 150 lb | 50 – 68 kg |
| 5’6” (168 cm) | 115 – 154 lb | 52 – 70 kg |
| 5’7” (170 cm) | 118 – 159 lb | 54 – 72 kg |
| 5’8” (173 cm) | 122 – 164 lb | 55 – 74 kg |
| 5’9” (175 cm) | 125 – 169 lb | 57 – 76 kg |
| 5’10” (178 cm) | 129 – 174 lb | 58 – 79 kg |
| 5’11” (180 cm) | 133 – 179 lb | 60 – 81 kg |
| 6’0” (183 cm) | 136 – 184 lb | 62 – 83 kg |
| 6’1” (185 cm) | 140 – 189 lb | 64 – 86 kg |
| 6’2” (188 cm) | 144 – 194 lb | 65 – 88 kg |
| 6’3” (191 cm) | 148 – 199 lb | 67 – 90 kg |
| 6’4” (193 cm) | 152 – 205 lb | 69 – 93 kg |
These are rounded estimates for the BMI 18.5–24.9 band, calculated from the standard BMI formula at the listed height. A healthy weight is a range, not a single target — where you sit within it (or slightly outside it) depends on your muscle mass, frame, and overall health markers.
BMI cutoffs for Asian and South-Asian adults
The standard BMI cutoffs (overweight at 25, obesity at 30) were derived largely from studies of European-ancestry populations. In 2004, a WHO Expert Consultation reviewed data across South, East, and Southeast Asian populations and reported that cardiometabolic risk — especially type 2 diabetes and cardiovascular disease — rises at BMIs several points below the standard thresholds. At the same BMI, many Asian populations carry more visceral abdominal fat and less lean muscle mass than European populations, which shifts the risk curve leftward.
The consultation recommended action thresholds of BMI 23 for overweight and 27.5 for obesity in these groups, alongside the standard cutoffs for the general population. In U.S. practice, the American Diabetes Association applies a matching principle: it recommends screening Asian Americans for type 2 diabetes at BMI 23 or above, versus the standard 25 or above for the wider population.
| Category | Standard BMI | Asian BMI |
|---|---|---|
| Healthy weight | 18.5 – 24.9 | 18.5 – 22.9 |
| Overweight | 25.0 – 29.9 | 23.0 – 27.4 |
| Obesity | 30.0 and above | 27.5 and above |
If you have South Asian, East Asian, or Southeast Asian ancestry, ask your clinician which cutoff set they apply — U.S., UK, Singaporean, and Indian guidelines increasingly use the lower thresholds for these populations.
BMI for teens and children (under 20)
BMI is calculated the same way for teens and children as for adults, but the adult healthy range of 18.5–24.9 does not apply below age 20. Growing bodies change composition and proportion year by year, so a single fixed number cannot describe a healthy weight across all ages and both sexes.
Instead, clinicians read a child or teen’s BMI against BMI-for-age percentiles on the CDC growth charts, which are age- and sex-specific:
- Below the 5th percentile — underweight
- 5th to 84th percentile — healthy weight
- 85th to 94th percentile — overweight
- 95th percentile or higher — obesity
- 120% of the 95th percentile or higher — severe obesity
A practical note for parents: do not calculate your teen’s BMI with an adult calculator and interpret the number by the adult categories. The number itself can be identical to an adult’s, but the meaning is different at 14 than at 40. Use the CDC’s dedicated child and teen BMI calculator or ask your pediatrician.
BMI in older adults (65+)
BMI’s healthy range was validated mostly in middle-aged adults. In older adults, the picture shifts in two ways that matter.
First, the “obesity paradox”: a 2014 meta-analysis by Winter and colleagues (J Nutr Health Aging 18:711) pooled cohort studies of adults aged 65 and over and found the lowest all-cause mortality at BMI 25–29.9 — the standard “overweight” band. Rather than harming survival in this age group, a modest weight reserve appears protective, likely because it buffers acute illness, muscle loss, and unintended weight loss.
Second, sarcopenic obesity: a “normal” BMI in an older adult can conceal a body composition of low muscle mass and higher body fat. The scale looks fine while function has quietly eroded. Waist circumference, grip strength, and usual gait speed are more predictive of independence and mortality risk in this age group than BMI alone.
Practical implication: a 70-year-old with a BMI of 27, good grip strength, and independent mobility is not automatically “overweight” in a clinically meaningful sense. Discussing goals with a clinician who accounts for muscle mass and function — not only weight — is more useful than pushing a number back into the adult 18.5–24.9 range.
BMI by sex and age — what changes
BMI uses the same formula and the same 18.5–24.9 healthy range for all adults regardless of sex. What differs is what a given BMI actually means under the skin. At the same BMI, women on average carry more body fat than men, and men carry more lean muscle and skeletal mass. So a 5’8” man and a 5’8” woman who both come in at BMI 24 have meaningfully different body composition — yet both land in the same “healthy” bucket. That mismatch is one of the biggest reasons BMI is best read as a starting point, not a diagnosis.
Age changes the picture too. After about 30, adults typically lose 3–8% of muscle mass per decade if they are not resistance-training, while body fat slowly creeps up even when the scale stays still. The practical result: an older adult at BMI 23 may carry the same body-fat percentage as a younger adult at BMI 26. That is one reason BMI cut-offs are not adjusted for older age groups but body-fat targets are. For a more direct read on what your body is actually made of, use BMI in combination with body fat percentage and a waist measurement — together they catch most of what BMI alone can miss.
What to do at each BMI category
Your BMI category is a prompt, not a prescription. Here is the practical next step for each band.
Underweight (BMI below 18.5)
A BMI under 18.5 is worth a conversation with a clinician, especially if the drop has been recent or unexplained. Possible causes include underlying thyroid or digestive conditions, undereating, or excessive training relative to intake. The goal here is a small, structured calorie surplus (roughly 250–500 kcal above maintenance), built around adequate protein and progressive resistance training to add lean mass rather than just fat. Crash gaining works no better than crash dieting.
Healthy weight (BMI 18.5–24.9)
The job here is maintenance, not loss. Anchor habits that hold the line for the long run: enough protein for weight loss and maintenance (roughly 0.7–1.0 g per pound of bodyweight), 2–3 sessions a week of strength training, daily walking, and a sleep target you actually hit. People who stay weight-stable for years almost always do so by guarding muscle mass and movement habits, not by perpetually dieting.
Overweight (BMI 25.0–29.9)
A modest calorie deficit (roughly 300–500 kcal below maintenance) paired with protein and resistance training is the highest-leverage move. Most adults at this BMI can produce 0.5–1.0 lb of weekly loss without extreme restriction. Start with how many calories to eat to lose weight for body-size-based ranges, and use the TDEE calculator and beginner deficit guide to set a sustainable target.
Obesity (BMI 30 and above)
At a BMI of 30 or higher (Class I obesity), the data favors stepping up the support level: structured behavioral programs work, and prescription options become clinically appropriate. Start with a structured plan, but talk with a clinician about medical weight-loss programs and whether GLP-1 medications are a fit — current U.S. guidance generally supports GLP-1 prescribing at BMI 30+, or BMI 27+ with a weight-related condition. For Class II (35+) and Class III (40+) obesity, weight-loss surgery delivers larger and more durable results than diet or medication alone; the bariatric surgery options compared guide walks through the main procedures and who they suit.
What to do next based on your BMI category
If you want a compact, category-by-category reference for the single most useful next step, this is it. Numbers are conservative and reflect current U.S. obesity-medicine guidance.
- Underweight (BMI < 18.5). Book a clinician visit if the loss was unintentional. Ask them to screen for thyroid disease, digestive absorption issues, and eating disorders. If the low BMI is longstanding and stable, the fix is a structured 250–500 kcal daily surplus with resistance training so the added weight is muscle, not just fat.
- Healthy weight (18.5–24.9). Maintain with the U.S. Physical Activity Guidelines target — 150 minutes of moderate-intensity movement per week plus 2 strength sessions — and use waist circumference (under 40 in for men, under 35 in for women) plus a routine blood-marker check for further screening.
- Overweight (25.0–29.9). Target a 5–10% weight loss. In the Diabetes Prevention Program (2002), that magnitude of loss cut type 2 diabetes risk by 58% over 3 years. A ~500 kcal daily deficit and adequate protein is the practical starting point — see weight loss meal plan and exercise for weight loss.
- Obesity class I (30.0–34.9). Same 5–10% loss target, but the support level goes up. You are inside the FDA’s on-label BMI window for GLP-1 medications (BMI ≥ 30, or ≥ 27 with a comorbidity such as type 2 diabetes, hypertension, or sleep apnea). See GLP-1 medications compared for the current options.
- Obesity class II (35.0–39.9) / class III (≥ 40.0). Combined care usually wins here: behavioural program + GLP-1 medication + consideration of bariatric surgery, which is on-label at BMI ≥ 40 or BMI ≥ 35 with a significant comorbidity. See bariatric surgery options compared and bariatric surgery vs GLP-1 medications for how the two paths compare.
The limitations of BMI (important)
BMI is a screen, not a diagnosis, and it is honest about being a blunt instrument. Here is where it falls short:
- It does not distinguish muscle from fat. BMI only knows your total weight, so a lean, muscular person can land in the “overweight” or even “obese” range despite having low body fat. Research analyzing thousands of adults found that BMI has high specificity but poor sensitivity for excess body fat — meaning a normal BMI often misses people who actually carry too much fat. To check composition directly, see body fat percentage: how to measure it and healthy ranges, or run a home estimate with the free body-fat percentage calculator using the U.S. Navy tape method. If you want to compare BMI’s healthy-range readout against the older single-number “ideal weight” figures used in clinical dosing, the ideal weight calculator runs the four historical formulas (Hamwi, Devine, Robinson, Miller) alongside the same 18.5–24.9 BMI band.
- It ignores where fat is stored. Fat around the abdomen (visceral fat) carries more metabolic risk than fat on the hips and thighs, but BMI treats all weight the same. Pair BMI with a distribution measure — the waist-to-hip ratio calculator uses the WHO 2008 sex-specific cutoffs and adds a waist-to-height readout in the same tool.
- It is less accurate for older adults. Aging tends to reduce muscle mass and shift fat distribution, so an “acceptable” BMI in an older adult can hide a higher body-fat percentage. The lowest-mortality BMI also shifts upward after 65 — see weight loss for older adults for the BMI obesity paradox and the function-first endpoints that replace BMI as the primary risk signal.
- It can be misleading during pregnancy. Pregnancy changes weight and body composition in expected ways, so standard BMI categories do not apply. Weight goals in pregnancy should be set with a clinician.
- Population cut-offs are not one-size-fits-all. A WHO expert consultation found that some Asian populations face elevated risk of type 2 diabetes and cardiovascular disease at BMIs below the standard 25 overweight threshold, leading to lower action points (often around 23) in some guidelines. Risk relationships differ across ethnic groups.
The takeaway: a BMI outside the healthy range is a useful prompt to look closer, not a final verdict. Pair it with waist size, blood pressure, blood sugar, cholesterol, fitness, and how you actually feel.
What to do next
If your BMI suggests you would benefit from losing weight, the next step is understanding the numbers that actually drive change — your energy balance, not just the scale.
- Find your maintenance calories. Estimate how many calories you burn in a day, then set a sensible deficit, with our TDEE and calorie deficit guide for beginners. It includes an interactive TDEE calculator that turns your numbers into a daily target.
- Set a daily calorie target. See practical, body-size-based ranges in how many calories to eat to lose weight.
- Turn a target into meals. Use a ready-made framework with our 7-day weight loss meal plan.
- Project a realistic timeline. See how long results take, and run the dates yourself, with how long it takes to lose weight.
Steady, sustainable change — a modest calorie deficit, enough protein, and regular activity — moves BMI in the right direction far more reliably than any crash approach.
Frequently asked questions
What is a healthy BMI? For adults aged 20 and over, the World Health Organization classifies a body mass index of 18.5 to 24.9 as the healthy-weight range. Below 18.5 is underweight, 25.0 to 29.9 is overweight, and 30.0 or above is the obesity range.
BMI is a screening tool, not a diagnosis — treat your number as one data point alongside waist size, blood markers, and how you feel.
Is BMI accurate? BMI is a useful population screen but an imperfect individual measure. It can misclassify very muscular adults, older adults with age-related muscle loss (sarcopenia), and some Asian populations whose cardiometabolic risk rises at BMIs below the standard 25 overweight cutoff.
Research finds BMI has high specificity but poor sensitivity for excess body fat — meaning a normal BMI can miss people who actually carry too much fat. Pair BMI with a direct body-composition measure when it matters.
What is my ideal weight for my height? Your ideal weight range is the one that puts your BMI between 18.5 and 24.9 for your height. Someone who is 5’6” has a healthy range of roughly 115 to 154 lb (52 to 70 kg). Enter your own height in the calculator on this page for your personal range.
Where you land inside that range depends on your muscle mass, frame, and other health markers — a personal goal weight is not always the middle of the healthy band.
How is BMI calculated? BMI equals your weight in kilograms divided by your height in metres squared (kg/m²). In imperial units the formula is weight in pounds divided by height in inches squared, multiplied by 703. The calculator handles both unit systems for you.
Does a high BMI mean I am unhealthy? Not necessarily. A high BMI flags higher statistical risk for conditions like type 2 diabetes and heart disease across a population, but individual health depends on body composition, fitness, waist circumference, blood pressure, blood sugar, and lipids. If your BMI is outside the healthy range, use it as a prompt to look at those other markers and talk with a clinician — not as a final judgment.
What is a healthy BMI for my height? A healthy BMI is 18.5 to 24.9 for all adult heights. The actual weight that produces a healthy BMI scales with height — about 89 to 119 lb at 4’10”, roughly 115 to 154 lb at 5’6”, and around 152 to 205 lb at 6’4”. The healthy-weight-by-height lookup table above shows the range at every inch from 4’10” to 6’4”.
Is BMI accurate for muscular people? No. BMI only knows your height and your total weight, so it cannot tell muscle and fat apart. Lean, well-trained athletes can land in the “overweight” or even “obese” range despite carrying very little body fat. If you carry significant muscle, pair BMI with a direct composition measurement — see body fat percentage: how to measure it and healthy ranges for the methods that actually distinguish fat from lean mass.
What BMI qualifies for weight loss medication or surgery? Current U.S. guidance generally supports GLP-1 weight-loss medications at a BMI of 30 or above, or 27 or above when paired with a weight-related condition such as type 2 diabetes, hypertension, or obstructive sleep apnea. Bariatric surgery is typically considered at a BMI of 40 or above, or 35 or above with a significant comorbidity — see the bariatric surgery options compared guide for what each procedure involves. Final eligibility depends on your clinician and your insurance, not BMI alone.
Sources
- Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults. NHLBI Evidence Report (1998).
- Appropriate body-mass index for Asian populations and its implications for policy and intervention strategies. The Lancet (2004).
- Accuracy of body mass index in diagnosing obesity in the adult general population. International Journal of Obesity (2008).
- Body mass index as a phenotypic expression of adiposity: quantitative contribution of muscularity in a population-based sample. International Journal of Obesity (2009).
- Winter JE, MacInnis RJ, Wattanapenpaiboon N, Nowson CA. BMI and all-cause mortality in older adults: a meta-analysis. Journal of Nutrition, Health & Aging 18(8):711–722 (2014).
- About Child & Teen BMI. Centers for Disease Control and Prevention (2024 update).
- Knowler WC, Barrett-Connor E, Fowler SE, et al. Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. New England Journal of Medicine 346:393–403 (2002). (Diabetes Prevention Program.)