A BMI calculator estimates weight category using height and weight. It's a quick screening tool, not a diagnosis. For weight management, combine BMI with TDEE tracking and food scanning.
Quick Answer
- • BMI calculator: Estimates if weight is healthy using height & weight
- • Free & instant: No signup, results in seconds
- • What's next: Check TDEE and scan meals
Last updated: 2026
BMI Calculator: Is Your Weight Healthy? (Free Instant Results)
Your BMI (Body Mass Index) tells you if your weight is healthy for your height. Being overweight increases risk of diabetes, heart disease, and joint problems. Being underweight weakens immunity and bone health. Use this free BMI calculator to know where you stand — then take action.
⚕️ Why Your BMI Matters for Long-Term Health
- • BMI 25-29.9 (overweight) = 20% higher disease risk
- • BMI 30+ (obese) = 50-100% higher risk of diabetes, heart disease
- • BMI under 18.5 = weak immune system, bone fractures, fertility issues
Knowing your BMI is the first step to taking control of your health.
📊 Who Should Check Their BMI?
- ✓ Anyone starting a weight loss journey
- ✓ People with family history of diabetes/heart disease
- ✓ Adults tracking health metrics annually
- ✓ Athletes monitoring body composition
- ✓ Seniors managing age-related weight changes
- ✓ Anyone curious about health status
Frequently Asked Questions
What is BMI?
BMI (Body Mass Index) is a measurement that uses your height and weight to determine if your weight is healthy. It's calculated by dividing your weight in kilograms by your height in meters squared (kg/m²). Use alongside body fat percentage for complete picture.
What is a healthy BMI range?
A healthy BMI range for adults is typically 18.5 to 24.9. Below 18.5 is considered underweight, 25-29.9 is overweight, and 30+ is obese. If overweight, calculate your ideal weight target.
How accurate is BMI for determining health?
BMI doesn't distinguish muscle from fat. Athletes may have "high" BMI but low body fat. Combine with calorie tracking and diet quality for full health picture.
How can I improve my BMI?
If BMI is high, create a calorie deficit by eating 500 below your TDEE. Track meals with AI food scanning. If BMI is low, eat at surplus and track protein intake.
Should I use BMI or body fat percentage?
Both are useful. BMI is quick and easy. Body fat percentage is more accurate for body composition. Check both, then use premium tracking tools to monitor progress weekly.
What Is BMI? Definition, History, and What It Measures
Body Mass Index (BMI) is a number derived from your height and weight that places you into a weight category. It was developed in the 1830s by Belgian astronomer and statistician Adolphe Quetelet, originally as a population-level measure called the Quetelet Index.
Today, BMI is used by the World Health Organization (WHO), the Centers for Disease Control and Prevention (CDC), and the National Institutes of Health (NIH) as a simple screening tool for weight-related health risk. It does not measure body fat directly, but it correlates moderately well with body fat percentage for most adults.
BMI is a starting point, not a diagnosis. A high BMI prompts further assessment, such as body fat percentage, waist circumference, and metabolic markers, before any health conclusion is drawn.
The BMI Formula: Metric and Imperial Equations
Metric Formula
BMI = weight (kg) ÷ height (m)²
Imperial Formula
BMI = 703 × weight (lb) ÷ height (in)²
Worked example (metric): A person who weighs 70 kg and is 175 cm (1.75 m) tall.
BMI = 70 ÷ (1.75)²
BMI = 70 ÷ 3.0625
BMI = 22.9 (Healthy weight)
Source: WHO BMI classification; CDC adult BMI calculator.
BMI Categories (WHO / CDC Classification)
The following categories apply to adults age 20 and older, regardless of sex:
| Category | BMI Range | Health Note |
|---|---|---|
| Underweight | Below 18.5 | Increased risk of nutrient deficiency, bone loss |
| Healthy weight | 18.5 – 24.9 | Lowest risk of chronic disease |
| Overweight | 25.0 – 29.9 | Moderately increased risk |
| Obese (Class I) | 30.0 – 34.9 | High risk of type 2 diabetes, heart disease |
| Obese (Class II) | 35.0 – 39.9 | Very high risk |
| Obese (Class III) | 40.0 and above | Extremely high risk; severe obesity |
BMI Reference Chart by Height and Weight
Use this chart to find the weight ranges that correspond to each BMI category at common heights.
| Height | Underweight | Healthy (18.5–24.9) | Overweight (25–29.9) | Obese (30+) |
|---|---|---|---|---|
| 150 cm (4'11") | Below 41.6 kg | 41.6 – 56.2 kg | 56.3 – 67.4 kg | 67.5+ kg |
| 160 cm (5'3") | Below 47.4 kg | 47.4 – 63.9 kg | 64.0 – 76.7 kg | 76.8+ kg |
| 170 cm (5'7") | Below 53.5 kg | 53.5 – 72.3 kg | 72.4 – 86.7 kg | 86.8+ kg |
| 175 cm (5'9") | Below 56.7 kg | 56.7 – 76.5 kg | 76.6 – 91.8 kg | 91.9+ kg |
| 180 cm (5'11") | Below 59.9 kg | 59.9 – 80.8 kg | 80.9 – 97.0 kg | 97.1+ kg |
| 185 cm (6'1") | Below 63.3 kg | 63.3 – 85.3 kg | 85.4 – 102.4 kg | 102.5+ kg |
| 190 cm (6'3") | Below 66.8 kg | 66.8 – 90.0 kg | 90.1 – 108.0 kg | 108.1+ kg |
Values are approximate. Calculate your exact BMI using the tool above.
Limitations of BMI: When It Gets It Wrong
BMI is a useful screening tool, but it has well-documented limitations. It measures weight relative to height but cannot see what that weight is made of.
- Athletes and muscular individuals: High muscle mass inflates BMI without excess fat. A lean bodybuilder can register as overweight or obese.
- Older adults: BMI does not account for age-related muscle loss. An older adult may have a normal BMI but high body fat and low muscle.
- Pregnancy: BMI categories do not apply during pregnancy. Weight gain is expected and healthy.
- Ethnicity: Body fat distribution and health risk vary by ethnicity. Some populations face diabetes risk at lower BMI thresholds than the standard categories suggest.
- Children and teens: BMI is interpreted using age- and sex-specific percentile charts, not the adult categories.
For a more complete picture, pair BMI with body fat percentage and waist circumference.
BMI vs Body Fat Percentage: Why Both Matter
BMI and body fat percentage measure different things. BMI tells you your weight category; body fat percentage tells you what your weight is made of.
| Measure | What It Captures | Best For |
|---|---|---|
| BMI | Weight relative to height | Quick screening, population-level risk |
| Body fat % | Actual fat mass vs lean mass | Athletes, body composition tracking |
For most adults, BMI is a good starting point. If you are muscular, an athlete, or tracking a body recomposition goal, check your body fat percentage alongside BMI for a more accurate picture.
What to Do With Your BMI Result: Next Steps by Category
Your BMI result is a starting point for action, not a final verdict. Here is what to do based on your category:
Underweight (< 18.5)
Focus on nutrient-dense foods and strength training. Track calories to ensure a surplus. Consult a healthcare provider to rule out underlying causes.
Healthy (18.5–24.9)
Maintain your current habits. Check your TDEE to understand your maintenance calories, and monitor annually.
Overweight (25–29.9)
Create a moderate calorie deficit of 300 to 500 calories below TDEE. Increase protein and fiber, add regular activity, and track progress weekly.
Obese (30+)
A structured weight loss plan is recommended. Calculate your calorie deficit, consider increasing NEAT, and consult a healthcare provider for a personalized approach.
For any category, tracking your daily calories with a calorie calculator and understanding your TDEE gives you the tools to move toward a healthier weight.
BMI Calculator FAQs
Disclaimer: This BMI calculator provides estimates for educational purposes only and is not medical advice. BMI is a screening tool, not a diagnostic measure. Individual health assessments require evaluation by a qualified healthcare provider. Consult a physician before starting any weight loss or weight gain program.
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