Adult BMI Calculator for Men & Women

Use the Adult BMI Calculator

Enter your height and weight to calculate BMI instantly with WHO categories. This adult BMI calculator supports metric and US units for quick, clear results.

How to Use Adult BMI Calculator for Men & Women

1. Step 1: Choose units

   Select Metric (cm, kg) or US (ft/in, lb) at the top of the tool.

2. Step 2: Enter height

   Type your height. Use centimeters (Metric) or feet and inches (US).

3. Step 3: Enter weight

   Type your current body weight in kilograms or pounds.

4. Step 4: Read your BMI

   Your BMI and WHO category appear instantly with a color-coded scale.

5. Step 5: Check healthy range

   See the healthy weight range for your height and adjust inputs as needed.

Key Features

• Adult BMI calculation
• WHO classification categories
• Metric and imperial units
• Healthy weight range by height
• Color-coded results

Understanding Results

Formula

Body Mass Index (BMI) compares your weight to your height using a simple equation. In metric units, BMI = weight (kg) / [height (m)]². In US units, BMI = 703 × weight (lb) / [height (in)]². The same result is shown regardless of the unit system — only the inputs differ. We round BMI to one decimal to keep results readable while preserving precision.

Reference Ranges & Interpretation

For adults aged 20 and over, the World Health Organization (WHO) defines categories used worldwide for screening. Underweight: <18.5. Healthy weight: 18.5–24.9. Overweight: 25.0–29.9. Obesity class I: 30.0–34.9. Obesity class II: 35.0–39.9. Obesity class III: ≥40. Your category helps you and your care team decide whether additional assessment is warranted.

The calculator also estimates a healthy weight range for your height based on BMI 18.5–24.9. This is a practical target zone you can use to set goals alongside other metrics like waist circumference, fitness capacity, and body composition.

Assumptions & Limitations

BMI is a screening tool, not a diagnosis. It does not directly measure body fat, fat distribution, or fitness. Muscular individuals (e.g., strength athletes) may have a higher BMI despite healthy body fat. Older adults may carry the same BMI with different composition. BMI is not designed for children, teens, pregnancy, or certain medical conditions.

For more context, consider pairing BMI with waist-to-height ratio, body-fat percentage, and activity markers. Learn more from the CDC’s BMI guidance and the WHO overview on overweight and obesity.

Complete Guide: Adult BMI Calculator for Men & Women

Use the adult BMI calculator to find your BMI with WHO categories. Enter metric or imperial units to see your status and BMI ranges quickly and clearly.

Use this adult BMI calculator as a quick screening step — not a diagnosis. It helps you notice trends, set realistic targets, and track changes alongside other measures like waist size, fitness level, and how you feel day to day.

What is BMI?

Body Mass Index (BMI) is a long‑standing, widely used way to compare weight to height. Instead of interpreting a raw number on the scale, BMI normalizes your weight for your stature, offering a single value that correlates with population‑level health risk. It is not perfect — it does not directly measure body fat — but it is consistent, inexpensive, and practical.

In clinical practice and public health, BMI is often the first pass. It helps flag potential risk so that a clinician can decide if further evaluation is needed, such as checking waist circumference, blood pressure, blood lipids, A1C, and fitness markers. For everyday users, BMI can help track progress over months and years.

How the adult BMI calculator works

Enter your height and weight in either metric (centimeters and kilograms) or US (feet, inches, and pounds). The calculator converts everything to metric under the hood and applies the standard formula: weight in kilograms divided by height in meters squared. We round to one decimal place to balance readability with precision.

You will see a color‑coded category based on World Health Organization (WHO) adult cut‑offs, plus the healthy weight range for your height (BMI 18.5–24.9). That range gives you a practical target zone. If you are outside the range, your plan might involve gradual changes to nutrition, activity, sleep, and stress management.

WHO adult BMI categories

The WHO categories are used globally for adults aged 20 and older. Underweight: less than 18.5. Healthy weight: 18.5 to 24.9. Overweight: 25.0 to 29.9. Obesity class I: 30.0 to 34.9. Obesity class II: 35.0 to 39.9. Obesity class III: 40.0 and higher. These boundaries help standardize communication and screening; they are not a verdict on your health.

Two people can share the same BMI with different body compositions. That is why context matters. An endurance runner and a powerlifter may land in different categories for different reasons. When in doubt, look at the full picture and the trends over time.

Healthy weight range for your height

Our calculator displays a weight range that corresponds to BMI 18.5–24.9 for your height. If your current weight is above the upper limit, bringing weight toward the range generally reduces cardiometabolic risk. If it is below the lower limit, you may benefit from weight gain, strength training, or evaluation for underlying issues — especially if there are unexpected changes in appetite or energy.

If you are planning, pair this with a daily energy plan. Try our calorie calculator and TDEE calculator to estimate maintenance calories, and consult the BMR calculator to understand your resting energy needs.

Limitations of BMI (and when it misleads)

BMI does not distinguish between fat mass and lean mass, nor does it tell you where fat is distributed. Muscular individuals can be labeled “overweight” or “obese” even with low body fat; conversely, a normal BMI can occur with high visceral fat. Ethnicity, age, and sex can influence risk at the same BMI. Pregnancy and certain conditions also require different assessment tools.

For a fuller picture, look at waist‑to‑height ratio and body‑fat percentage. Central adiposity (more fat around the abdomen) is more strongly linked with metabolic risk than total BMI alone. Our tools for waist‑to‑height ratio and body fat percentage can help you add this context.

BMI versus body fat and waist measures

BMI is excellent for a quick screen, especially across large groups. Body fat percentage adds more resolution: it reflects the proportion of your body that is fat versus lean tissue. When paired with waist measures, you get a three‑part view — size for height (BMI), composition (body fat), and distribution (waist). This combination maps more closely to health risk than any one measure alone.

If your BMI is in the overweight or obesity ranges, a smaller waist relative to height and a decent fitness level still shift risk in a favorable direction. This is empowering: you have multiple levers to pull beyond the scale number.

Setting goals with BMI: practical strategies

Begin by noting your current BMI and the healthy range for your height. If your goal is weight loss, aim for gradual change — about 0.25–0.75% of body weight per week for most adults. That pace tends to protect muscle, support adherence, and reduce rebound risk. A simple framework is a modest calorie deficit, adequate protein, regular activity, and consistent sleep.

Try our weight loss calorie calculator to plan a sustainable deficit. If you are underweight, the inverse applies: modest surplus, progressive resistance training, and a focus on whole‑food energy sources can help you move toward the healthy range.

Diet, activity, and recovery: small habits that compound

Most people do best with structure that is flexible, not rigid. Build your plate around lean proteins, colorful produce, whole‑grain starches, and healthy fats. Keep hunger and energy stable by pairing protein with fiber at meals. Hit at least the minimum activity guidelines, then layer in strength and cardio you enjoy. Guard your sleep routine and manage stress with short, repeatable practices.

• Protein target: consider 1.6–2.2 g/kg/day, adjusted to preference.
• Activity baseline: 150+ minutes/week of moderate cardio, plus 2–3 strength sessions.
• Sleep: aim for a regular 7–9 hour window; keep wake time consistent.
• Environment: make the default choice the easy choice; stock supportive foods.

For a more tailored energy plan, combine BMI with your basal and total daily needs. See the BMR calculator and TDEE calculator for guidance on daily calories. If body composition is your priority, the ideal body weight calculator may help you sense check long‑term targets.

Frequently confused points about BMI

Rounding can cause small differences between tools. Some apps display two decimals; others show one. Height entry (centimeters versus meters, or whether you counted shoes) also shifts results slightly. These differences do not change your overall category or next steps — what matters most is trend and consistency.

Another common confusion: “normal” BMI does not guarantee optimal health, and “overweight” does not doom you. Move more, eat well, and sleep regularly — you can improve your health regardless of your starting BMI. Treat BMI as one useful lens among many.

Interpreting BMI changes over time

BMI is most helpful as a trend rather than a single snapshot. Day‑to‑day shifts in water, glycogen, and gut contents can move the scale without real changes in body composition. Compare weekly or monthly averages taken under similar conditions (same scale, time of day, and clothing). For many adults, a steady change of roughly 0.25–0.75% body weight per week reflects a sustainable pace; faster swings often reflect water shifts or overly aggressive dieting.

Context matters, too. If strength training raises lean mass, BMI may hold steady while waist measurements shrink and performance improves — a positive outcome that BMI alone might miss. During maintenance, a flat BMI paired with stable waist and energy levels usually signals you are on track. If BMI moves unexpectedly, check inputs first (height entry, unit selection, clothing, scale calibration) before changing your plan.

Use the adult BMI calculator alongside other metrics: waist‑to‑height ratio, progress photos, training logs, and sleep consistency. That fuller picture helps you make adjustments you can sustain, not just hit a number once. For clinical questions, bring several weeks of readings to a clinician — trends tell the story far better than a one‑off value.

Related calculators and next steps

Explore more tools to add context or plan your next step:

• Body Fat Percentage Calculator — estimate body composition beyond BMI.
• Waist‑to‑Height Ratio Calculator — screen central adiposity risk.
• BMR Calculator — understand your resting energy needs.
• TDEE Calculator — estimate daily maintenance calories.
• Calorie Calculator — plan intake for loss, maintenance, or gain.
• Ideal Body Weight Calculator — compare multiple IBW formulas.

References

• Centers for Disease Control and Prevention. About Adult BMI.
• World Health Organization. Obesity and overweight.

Frequently Asked Questions