BMI Calculator
Body Mass Index Analyzer – calculate your BMI instantly, based on World Health Organization standards, with ideal weight, calorie needs and health tips.
Enter Your Details
Choose your unit system, then enter your age, height and weight. The result below updates as you type; the default example is a 25-year-old male, 175 cm, 70 kg.
| Height (ft / in) | |
Your BMI Results
These values are calculated from your details using the formulas listed below. The gauge marker shows where your BMI falls between 15 and 40.
| BMI | 22.9 |
|---|---|
| Category | Healthy Weight |
| Ideal Weight (kg) | 56.7–76.3 |
| BMI Prime | 0.91 |
| Daily Calories (TDEE) | 2,594 kcal |
| Body Fat % (estimated) | 17% |
| Weight Status | +3.5 kg above ideal |
| Protein (g/day) | 195 |
| Carbs (g/day) | 259 |
| Fat (g/day) | 86 |
Gauge scale 15 to 40: blue = underweight, green = healthy, yellow = overweight, orange and red = obese.
Personalized Health Tips
These tips change with your BMI category. They are general guidance, not medical advice.
| You are in the healthy BMI range (18.5–24.9) as defined by the WHO. Keep it up! |
| The WHO recommends 150–300 minutes of moderate aerobic activity weekly for adults. |
| Follow a balanced diet. Harvard's Healthy Eating Plate is an excellent evidence-based guide. |
| Prioritize 7–9 hours of sleep. Poor sleep disrupts metabolic hormones per NIH research. |
| Monitor your BMI quarterly. Consistent tracking helps maintain long-term healthy weight. |
BMI Reference Chart
This table shows the WHO BMI categories with their health risk. Your category is highlighted after you calculate. Asian populations may face elevated risk from BMI 23.
| Category | BMI Range | Health Risk |
|---|---|---|
| Underweight | < 18.5 | Moderate |
| Normal Weight | 18.5 – 24.9 | Low |
| Overweight | 25 – 29.9 | Moderate |
| Obese Class I | 30 – 34.9 | High |
| Obese Class II | 35 – 39.9 | Very High |
| Obese Class III | ≥ 40 | Extremely High |
Formulas & Scientific Methodology
All calculations use peer-reviewed formulas from internationally recognized health institutions. The source of each formula is listed in the References table.
| Calculation | Formula | Method |
|---|---|---|
| BMI | BMI = Weight (kg) ÷ Height² (m²) | Standard WHO/NIH formula (NIH / NHLBI) |
| BMR (Male) | 10×W + 6.25×H − 5×A + 5 | Mifflin–St Jeor Equation, published on PubMed (1990) |
| BMR (Female) | 10×W + 6.25×H − 5×A − 161 | Mifflin–St Jeor Equation, published on PubMed (1990) |
| Body Fat % | (1.2 × BMI) + (0.23 × Age) − (10.8 × Gender) − 5.4 | Deurenberg Formula (Gender: male = 1, female = 0) |
| TDEE | TDEE = BMR × Activity Factor (1.2 – 1.9) | Harris-Benedict activity multiplier, standard in clinical nutrition |
Frequently Asked Questions
These are the most common questions about BMI, ideal weight, calories and children. Find your question in the table and read the answer next to it.
| Question | Answer |
|---|---|
| Is this BMI calculator free to use? | Yes, our BMI calculator is 100% free with no login required. We follow a zero data storage policy to protect your privacy. |
| Which guidelines does this BMI tool follow? | The calculations are based on official guidelines from the WHO (World Health Organization) and NIH (National Institutes of Health). |
| What is BMI and how is it calculated? | BMI (Body Mass Index) measures body fatness from height and weight: BMI = kg ÷ m². Developed in the 1830s, it is the standard tool used by the World Health Organization (WHO), CDC, and NIH / NHLBI to classify weight status in adults and children worldwide. |
| What is a healthy BMI for adults? | Per the WHO and NIH, a healthy BMI for adults is 18.5 – 24.9. The Harvard T.H. Chan School of Public Health notes Asian populations may face elevated risk starting at BMI 23. Elderly adults often benefit from a slightly higher BMI of 23–28. |
| Is BMI accurate for athletes and bodybuilders? | BMI cannot distinguish fat from muscle — a known limitation acknowledged by the CDC. Muscular people may show high BMI despite low body fat. Our tool uses the Deurenberg formula (PubMed) which partially adjusts for this. For athletes, DEXA scans provide more accurate body composition data. |
| How do I find my ideal weight using BMI? | Ideal weight range uses the healthy BMI band (18.5–24.9): Min = 18.5 × height(m)², Max = 24.9 × height(m)². This method is endorsed by NIH's clinical obesity guidelines. Our calculator shows this range automatically after entering your details. |
| What is TDEE and how many calories do I need? | TDEE is your total daily calorie burn including activity. We use the Mifflin–St Jeor equation (PubMed, 1990), recognized as one of the most accurate by the Mayo Clinic. Eat at TDEE to maintain weight, 300–500 kcal below to lose fat, or 200–300 kcal above to gain muscle. |
| What BMI is considered obese? | BMI ≥ 30 is classified as obese by the WHO and CDC: Class I (30–34.9), Class II (35–39.9), Class III / Morbid (≥ 40). The Mayo Clinic confirms each class carries increasing risk for type 2 diabetes, cardiovascular disease, and sleep apnea. |
| Can I calculate BMI for children and teenagers? | Yes. For ages 5–17, BMI-for-age percentiles are used. Per the CDC Children's BMI tool: below 5th percentile = underweight; 5th–85th = healthy; 85th–95th = overweight; above 95th = obese. Our calculator supports ages 5–100 but always consult a pediatrician for children. |
Research & Trusted Sources
This tool is built on formulas from the world's most trusted health organizations and peer-reviewed journals. Open any source below to verify.
| Source | Title | What it covers | Link |
|---|---|---|---|
| WHO | World Health Organization — Obesity & BMI | Global BMI classification used in 190+ countries | who.int |
| NIH / NHLBI | National Heart, Lung & Blood Institute | Official US government BMI & obesity guidelines | nhlbi.nih.gov |
| CDC | Centers for Disease Control and Prevention | BMI for adults — definitions, limitations & healthy weight | cdc.gov |
| Mayo Clinic | Obesity: Diagnosis & Treatment | Clinical guidance on BMI, obesity classes & health risks | mayoclinic.org |
| Harvard University | T.H. Chan School of Public Health — BMI | Academic research on BMI as a health measure | hsph.harvard.edu |
| PubMed / NCBI | Mifflin–St Jeor Equation (1990) | Peer-reviewed formula used for our TDEE / calorie calculations | pubmed.ncbi.nlm.nih.gov |
| PubMed / NCBI | Deurenberg Body Fat % Formula | Validated equation for estimated body fat percentage | pubmed.ncbi.nlm.nih.gov |
| PubMed / NCBI | BMI Cut-Off Points for Asian Populations | Adjusted thresholds for South & East Asian individuals | ncbi.nlm.nih.gov |
About This BMI Calculator
Our free BMI calculator follows the exact formula endorsed by the World Health Organization, the National Institutes of Health (NIH), and the CDC. Whether you need BMI for insurance, a fitness goal, or a doctor's visit — this tool provides everything in one place.
Unlike basic calculators, ours provides: WHO-classified BMI category, ideal weight range, estimated body fat % via the Deurenberg formula, TDEE calories via the Mifflin–St Jeor equation, macro breakdown, and evidence-based health tips with sources.
Medical Disclaimer: BMI is a screening tool, not a diagnostic measure. Always consult a qualified healthcare professional for medical advice.