BMI Calculator
Calculate your BMI in seconds - see your category, chart position, and healthy weight range
About This BMI Calculator
Enter your height and weight for an instant BMI calculation, your category on the standard scale, and the healthy weight range for your height. Add your age and sex for plain-language context alongside the number. The page also covers what BMI actually measures, where it falls short, and what to do with the result - because a number without interpretation is not particularly useful. BMI is a screening tool, not a diagnosis. Use it as a starting point, not a conclusion.
Calculate Your BMI
Adult categories apply to ages 18+. For children, use growth charts.
Your BMI
22.7
Healthy weight (18.5 – 24.9)
Your position on the adult BMI scale
Healthy BMI range for your height
For your height, a BMI between 18.5 and 24.9 usually corresponds to roughly 125–169 lb. This is an estimate for screening, not a prescription.
BMI visual chart
Height and weight axes (imperial). Colored bands show BMI categories; the dot uses your current calculator inputs.
At 5'9" and 154 lbs, BMI is 22.7. Chart area: about 4'10"–6'6" height and 80–350 lbs; if you are outside that range, the dot sits on the nearest edge.
What to do next
If your BMI is in the healthy range (18.5-24.9): Maintain what is working - balanced nutrition, consistent movement, adequate sleep, and stress management. BMI in the healthy range does not guarantee good health, but it removes one population-level risk factor. Focus on the habits that got you here rather than optimizing the number further.
Formula and manual calculation
Metric steps
- Measure weight in kilograms.
- Measure height in meters (centimeters ÷ 100).
- Square height (m × m).
- Divide weight by squared height.
Imperial steps
- Measure weight in pounds.
- Measure height in total inches.
- Square height in inches.
- Multiply weight by 703, divide by squared height.
BMI chart & categories
Body Mass Index (BMI) relates height and weight. The table below shows standard adult BMI categories used for screening (CDC / WHO).
| BMI range | Classification | Notes |
|---|---|---|
| Below 18.5 | Underweight | May need clinical evaluation depending on symptoms. |
| 18.5 – 24.9 | Healthy weight | Typical screening target range for adults. |
| 25.0 – 29.9 | Overweight | Elevated risk at population level; context matters. |
| 30.0 – 34.9 | Obesity class I | Discuss risk factors and options with a provider. |
| 35.0 – 39.9 | Obesity class II | Higher average health risk; individualized care helps. |
| 40.0 and above | Obesity class III | Often managed with multidisciplinary support. |
These BMI categories reflect broad health-risk patterns across populations. BMI is a screening tool, not a diagnosis - your individual health depends on many factors beyond BMI.
BMI for Women vs Men
While the BMI scale is the same for both sexes, women and men can have the same BMI but different body composition and health implications.
Women
- Typically have 6–11% more body fat than men
- Healthy range: 18.5–24.9 (same scale)
- Higher body fat percentage can be normal and healthy
- Hormones affect weight distribution
- Pregnancy and menopause impact BMI
- Often carry weight in hips and thighs
Men
- Generally have more muscle mass
- Healthy range: 18.5–24.9 (same scale)
- Muscle weighs more than fat (BMI may underestimate fitness)
- Lower body fat percentage at the same BMI
- Testosterone influences body composition
- Often carry weight in the abdomen
Women with the same BMI as men typically have a higher body fat percentage, but that can be normal and healthy. Standard BMI ranges account for typical differences in body composition.
How BMI Changes With Age
While official BMI ranges (18.5–24.9 = healthy) stay the same regardless of age, research shows that slightly higher BMI may be acceptable - and even protective - as we get older.
Age-based BMI observations
| Age group | Ideal BMI range* | Notes |
|---|---|---|
| 19–24 years | 19–24 | Lower range often optimal for young adults |
| 25–34 years | 20–25 | Slight increase from early 20s |
| 35–44 years | 21–26 | Metabolism begins to slow |
| 45–54 years | 22–27 | Muscle mass naturally decreases |
| 55–64 years | 23–28 | Slight increase may be protective |
| 65+ years | 24–29 | Higher BMI sometimes linked to better outcomes in studies |
These are research-based observations, not official guidelines. The standard healthy range (18.5–24.9) still applies to all adults for screening. Always consult your doctor about your individual goals.
Why BMI trends higher with age
- Muscle loss: adults may lose 3–8% of muscle mass per decade after age 30
- Metabolism slows: basal metabolic rate decreases about 2% per decade
- Hormonal changes: reduced testosterone (men) and estrogen (women) affect body composition
- Protective effect: some studies suggest slightly higher BMI (25–27) in seniors may protect against illness and frailty
Healthy BMI Range
For most adults, a healthy BMI falls between 18.5 and 24.9. This band is associated with lower average risk of several chronic diseases at the population level than higher BMI bands. Your optimal target may still differ based on muscle mass, ethnicity-related risk (for example, some Asian populations use lower action thresholds), and medical history - use this page as education, not a diagnosis.
What Does Your Specific BMI Mean?
Search for your BMI value to see what it often means for screening. These are general patterns, not personal medical advice.
We highlight common search values. Your BMI falls on a continuum - use the category table above and your clinician for personalized interpretation.
When BMI Doesn’t Tell the Full Story
BMI is a useful screening tool, but it has important limits. Here is when BMI may not reflect your health status accurately.
BMI limitations
- Muscle vs fat: athletes may have a high BMI with low body fat.
- Bone density: denser bones can raise BMI without indicating poor health.
- Fat distribution: belly fat is riskier than hip/thigh fat, but BMI treats weight the same everywhere.
- Ethnicity: some groups face higher risk at lower BMI (for example, many Asian guidelines use action thresholds above 23).
- Older adults: muscle loss can make BMI look "healthy" while body composition worsens.
- Children: use pediatric BMI percentiles - not adult cutoffs.
- Pregnancy: BMI categories are not meant for pregnancy or the immediate postpartum period the same way.
Better alternatives or additions
- Waist circumference: belly fat indicator; common risk flags include roughly 40" (men) and 35" (women), per many clinical references.
- Waist-to-hip ratio: compares fat distribution.
- Waist-to-height ratio: waist should often be under half your height - simple rule of thumb used in some guidelines.
- Body fat percentage: calipers, bioimpedance, or DXA - each has tradeoffs.
- Labs and vitals: glucose, lipids, and blood pressure often matter as much as weight alone.
When to use alternatives
Use BMI for
- ✓Quick screening
- ✓Population trends
- ✓Tracking changes over time (with context)
- ✓Typical adults without unusual muscle mass
Favor add-on measures for
- ✓Athletes and bodybuilders
- ✓Many older adults
- ✓Pregnancy or postpartum (clinician-guided)
- ✓Children and teens
- ✓Anyone wanting a direct body-fat estimate
The AMA's 2023 Position Change - What It Means for You
In June 2023, the American Medical Association - the largest physician organization in the US - formally adopted a policy acknowledging that BMI is an imperfect measure that should not be used as the sole or primary indicator of health. The AMA's position now explicitly recognizes significant limitations related to race, ethnicity, sex, gender, and age, and that it should be used in conjunction with other valid measures of health risk.
This does not mean BMI is useless - it remains a simple, cost-free, widely standardized screening tool with well-documented population-level correlations with health outcomes. But the AMA's shift reflects what researchers have argued for years: a single number derived from height and weight cannot capture the complexity of individual health.
Practically, this means use your BMI result as one input among several, not as a verdict. Waist circumference, blood pressure, fasting glucose, and cholesterol are all more direct indicators of metabolic health than BMI. If your BMI is in a higher category but your other markers are healthy, your actual risk may be meaningfully lower than the BMI category implies.
FAQ
What is BMI?
Body Mass Index is a numerical value derived from your height and weight using the formula: weight (kg) divided by height (m) squared. It is a population-level screening tool that correlates - imperfectly - with body fat and associated health risks. It was developed by Belgian mathematician Adolphe Quetelet in the 1830s as a statistical tool for describing populations, and was adopted by public health organizations in the 20th century as a simple individual screening measure. It was never designed to diagnose individual health.
What is a good BMI for adults?
The standard healthy range is 18.5-24.9 for adults of all sexes. However, "good" depends on context - athletes may have BMIs above 25 due to muscle mass, some Asian populations face higher metabolic risk at lower BMIs, and slightly higher BMIs (25-27) may be protective for adults over 65. The healthy range is a population guideline, not a personal prescription.
How do I calculate my BMI?
Metric: divide your weight in kilograms by your height in meters squared. For a 70kg person who is 1.75m tall: 70 divided by (1.75 times 1.75) = 70 divided by 3.0625 = 22.9. Imperial: multiply your weight in pounds by 703, then divide by your height in inches squared. For a 154lb person who is 5'9" (69 inches): (154 times 703) divided by (69 times 69) = 108,262 divided by 4,761 = 22.7.
Does BMI differ for men and women?
The formula and categories are identical for men and women. However, at the same BMI, women typically have 6-11% more body fat than men - which is normal and healthy. Men with significant muscle mass may have elevated BMI with low body fat. The standard ranges do not adjust for sex, which is one of BMI's acknowledged limitations.
Does BMI change with age?
The formula does not change with age, but research suggests that slightly higher BMI may be acceptable - and even protective - for adults over 65, where low BMI is associated with muscle loss and frailty risk. Some researchers suggest the optimal BMI range shifts upward by approximately 1 unit per decade after age 35. This is observational data, not official guideline - the standard 18.5-24.9 range still applies for screening purposes.
What BMI is overweight? What BMI is obese?
Overweight: BMI 25.0-29.9. Obese class I: 30.0-34.9. Obese class II: 35.0-39.9. Obese class III: 40 and above. Underweight: below 18.5. These are CDC/WHO standard categories for adult screening.
Is BMI accurate?
As a population screening tool, yes - BMI correlates meaningfully with health outcomes at the group level. As an individual health measure, it has significant limitations. It cannot distinguish between muscle and fat, does not account for fat distribution, varies in accuracy across ethnic groups, and does not capture metabolic health directly. The 2023 AMA policy explicitly acknowledged these limitations and recommended using BMI alongside other measures rather than as a standalone diagnostic.
Can I have a high BMI and still be healthy?
Yes - this is well-documented. Athletes and heavily muscled individuals routinely have BMIs above 25 or even 30 with low body fat and excellent metabolic health. Conversely, someone with a "normal" BMI can have poor metabolic health if they have high visceral fat, elevated glucose, or unfavorable lipid profiles. BMI is a starting point for a conversation, not a conclusion about individual health.
Tips & Strategies
Track trends, not single measurements. BMI fluctuates daily with hydration, food timing, and clothing. A single reading means less than the direction of change over 3-6 months. Weigh yourself at the same time of day (morning, after bathroom, before food) for the most consistent comparison.
Waist circumference adds what BMI misses. Measure around your bare abdomen at the level of your navel, relaxed (do not hold your breath or pull it in). Above 40 inches for men or 35 inches for women signals elevated cardiovascular risk regardless of BMI category.
Muscle gain can raise BMI without raising health risk. If you are strength training consistently, your BMI may increase as muscle mass grows - this is not the same as gaining fat. Body fat percentage (see the Body Fat Calculator) is more meaningful for many people with active fitness routines.
BMI is not useful for tracking short-term diet results. A single week of dietary changes will not move your BMI meaningfully. It is a long-horizon metric - useful for tracking sustained lifestyle changes over months, not days.
Ethnicity-adjusted thresholds are worth knowing. For people of East or South Asian descent, many clinical guidelines use action thresholds of BMI 23 (overweight) and 27.5 (obese) rather than 25 and 30 - reflecting research showing higher metabolic risk at lower BMI.
Things Worth Knowing
- •The modern BMI formula dates to the 1830s (Lambert Adolphe Jacques Quetelet). It was meant to describe populations - not to label individuals as healthy or not.
- •Muscle weighs more than fat per volume. Athletes and very muscular people can have a high BMI without high body fat - so BMI is screening, not diagnosis.
- •Health risk at a given BMI varies by ancestry, waist size, and other factors. Some guidelines use lower action thresholds for Asian populations than for European populations.
- •For people under 18, BMI is interpreted with age- and sex-specific growth charts (for example CDC charts) - not the adult categories this calculator uses.