2026-05-24 · bmi, calculator, weight loss, healthy weight · 16 min read
Updated 2026-06-02
Written by Maya Patel
Maya Patel writes about sustainable weight loss through mindful eating, flexible routines, and evidence-based nutrition strategies. She shares practical meal planning, high-protein swaps, and balanced approaches that help busy households stay consistent without extremes.
BMI Calculator (Metric & Imperial): Weight Category and Healthy Weight Range by Height
Body mass index (BMI) is a quick screening number that compares your weight to your height. For most adults, a BMI of 18.5 to 24.9 is classed as a healthy weight, 25 to 29.9 is overweight, and 30 or above falls in the obesity range. Enter your height and weight below to get your BMI, your weight category, and the healthy-weight range for your height. BMI is a starting point, not a full picture of health — it does not measure body fat directly, so read the limitations section before acting on a single number.
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.
BMI is one of the most common entry points into thinking about weight, because it takes just two numbers you already know — your height and your weight — and turns them into a single figure you can compare against a standard scale. It is quick, free, and used by clinicians and researchers worldwide as a first screen. But “quick and standardized” is not the same as “complete,” and the rest of this page explains both how to read your number and where it falls short. 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 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.
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.
- 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. This is why waist circumference and waist-to-height ratio are useful companions to BMI.
- 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 most adults aged 20 and over, the World Health Organization classifies a body mass index of 18.5 to 24.9 as the normal or healthy weight range. Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 or above is the obesity range. BMI is a screening tool, not a diagnosis, so treat your number as one data point alongside waist size, blood markers, and how you feel.
Is BMI accurate? BMI is a useful population-level screen but an imperfect individual measure. It does not distinguish muscle from fat, ignores where fat is stored, and can misclassify very muscular people, older adults who have lost muscle, and some ethnic groups. Research shows BMI has high specificity but poor sensitivity for detecting excess body fat, so a normal BMI does not always mean low body fat. Use it as a starting point, not a verdict.
What is my ideal weight for my height? A simple, evidence-based estimate is the weight range that puts your BMI between 18.5 and 24.9 for your height. For example, someone who is 5 feet 6 inches has a healthy range of roughly 115 to 154 lb (52 to 70 kg). The calculator on this page shows your personal range automatically once you enter your height.
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).