BMI Calculator
Use this free BMI Calculator to quickly get accurate results in seconds, free and instantly offline with no signup required ever, trusted by professionals in Austin, Chicago, Miami, Denver, Seattle, and New York for reliable daily use without accounts, subscriptions, limits, or delays on any device for everyday personal and business workflows daily.
Calculate your Body Mass Index (BMI) with weight category, ideal weight range, BMI Prime, and health risk assessment.
Calculator Inputs
About BMI
Use this free BMI Calculator to quickly get accurate results in seconds, free and instantly offline with no signup required ever, trusted by professionals in Austin, Chicago, Miami, Denver, Seattle, and New York for reliable daily use without accounts, subscriptions, limits, or delays on any device for everyday personal and business workflows daily.
Body Mass Index (BMI) is a simple screening tool using weight and height to estimate body fat. While not diagnostic, it correlates with health risks across populations and is the standard first-line screen in primary care.
WHO Categories: Underweight (Severe <16, Moderate 16–16.9, Mild 17–18.4), Normal (18.5–24.9), Overweight (25–29.9), Obese Class I (30–34.9), Class II (35–39.9), Class III (≥40). Risk rises progressively from Increased to Extreme.
Ideal Weight Range: Based on BMI 18.5–25 for your height. Shows healthy weight window in kg. For example, at 175 cm the range is ~56.7–76.6 kg. This is a population guideline, not a personal prescription.
BMI Prime: Your BMI divided by 25 (upper normal limit). 0.9 means 10% below upper normal; 1.2 means 20% above. Useful for quick risk communication across heights.
Ponderal Index: Weight / height³. More accurate for very tall or short people where BMI over- or under-estimates. Track both if you are outside 160–190 cm.
Body Fat Estimate: Uses BMI + age + sex (Deurenberg formula). Rough estimate only — DEXA scan is gold standard, calipers and BIA scales are field alternatives. Women and older adults carry more fat at the same BMI.
Ethnic cutoffs: Some Asian guidelines use 18.5–22.9 normal and ≥23 overweight due to higher metabolic risk at lower BMI. Pacific Islander and athletic populations may be healthy at higher BMI. Apply the cutoff your clinician uses.
Athletes & muscle: BMI cannot distinguish muscle from fat. Lifters may read Overweight while lean. Pair BMI with waist-to-height ratio (<0.5), waist circumference, progress photos, and strength performance.
Safe change: Aim 0.5–1 kg per week via ~500–750 kcal daily deficit plus protein 1.6–2.2 g/kg and resistance training. Re-check BMI monthly, not daily, to filter water-weight noise.
Limitations: BMI does not diagnose health. It misses fat distribution, muscle, bone, pregnancy, edema, and age-related sarcopenia. Use with waist, body fat %, blood pressure, lipids, glucose, and clinical assessment.
Where it is used
Adult health screening and annual checkups, weight-loss and bulking goal-setting with target ranges, fitness coaching intake assessments, pre-employment and insurance health questionnaires, tracking progress alongside waist circumference and body-fat percentage, and flagging when to seek clinical evaluation for underweight or obesity.
How to use the BMI
- Weight — enter the value in kg (e.g. 70).
- Height — enter the value in cm (e.g. 175).
- Age (optional) — enter the value in years (e.g. 30).
- Sex (optional) — enter the value.
- Calculate — press the Calculate button to see the result instantly above.
Formula
BMI = weight(kg) / height(m)² Ideal: 18.5–25 BMI Prime = BMI / 25
Examples
Average Adult
Overweight
Athletic Build Check
Frequently Asked Questions
- Is BMI accurate for everyone?
- No. BMI doesn't distinguish muscle from fat. Athletes, elderly, and certain ethnic groups may have different health risks at the same BMI. Always combine with waist circumference, body fat %, and clinical evaluation.
- What is a healthy BMI range?
- WHO defines 18.5–24.9 as normal weight. Some Asian populations use 18.5–22.9 due to higher health risks at lower BMIs. Consult your healthcare provider for personalized targets.
- What is BMI Prime?
- Your BMI divided by 25 (upper limit of normal). BMI Prime of 1.0 = exactly at upper normal. 1.2 = 20% above normal. Useful for quick health risk assessment.
- How much weight should I lose/gain?
- The calculator shows weight change needed to reach BMI 25 (upper normal) or 18.5 (lower normal). This is a guideline — rate of change should be 0.5–1 kg/week for safety.
- Is this calculator suitable for children?
- No. Children use BMI-for-age percentiles (CDC growth charts), not fixed adult categories. Use a pediatric BMI percentile calculator.
- Why is my BMI normal but waist high?
- Normal-weight central obesity carries metabolic risk despite healthy BMI. Men >94 cm and women >80 cm waist should discuss lipids, glucose, and blood pressure with a clinician even with BMI 18.5–24.9.
- How often should I recheck BMI?
- Monthly under consistent conditions (morning, fasted, after toilet). Daily swings are water and glycogen. Pair with waist and 4-week weight trend for decisions.
- What should athletes use instead?
- Use body-fat % (DEXA, 7-site calipers, or validated BIA), waist-to-height ratio, progress photos, and performance. BMI is a screening entry point, not a body-composition tool.