Updated · Methodology: named formula library
BMI Calculator
Calculate your Body Mass Index (BMI) from height and weight. See where you fall on the BMI scale.
Your BMI is 25.8, which falls in the "Overweight" category. BMI is a screening tool, not a diagnostic measure.
Why This Calculation Matters
The BMI Calculator turns a well-known health formula into an instant lookup. It's most useful when you're tracking a number over time or comparing yourself against published reference ranges from bodies like the CDC, NIH, or WHO. Use it as one data point among many, not a diagnosis.
How to Use This Calculator
- Enter your values in the input fields, each one has a label and help text explaining what to type.
- Results appear instantly as you type; there's no "calculate" button to press.
- Change any input to compare scenarios side by side.
All math happens in your browser. Nothing you type is sent to a server, saved, or shared.
Reading Your Result
A single number tells you less than a trend. Track this value over weeks or months rather than obsessing over day-to-day variation. Hydration, sleep, and timing can all shift short-term readings without reflecting any real change.
What Is BMI?
Body Mass Index (BMI) is a screening tool that estimates body fat based on height and weight. It's calculated as weight (kg) / height (m)².
BMI Categories
- Underweight: Below 18.5
- Normal weight: 18.5-24.9
- Overweight: 25-29.9
- Obesity: 30 and above
Limitations
BMI doesn't distinguish between muscle and fat. Athletes and muscular individuals may have a high BMI without excess body fat. Waist circumference and body fat percentage are complementary measures.
Formula
Metric: BMI = kg / m². Imperial: BMI = (lb / in²) × 703. WHO categories: underweight <18.5, normal 18.5-24.9, overweight 25-29.9, obese ≥30.
Worked Example
A 5'10" (178 cm), 170 lb (77 kg) adult.
- Weight
- 77 kg
- Height
- 178 cm
- Result
- 24.3 (Normal weight)
BMI between 18.5 and 24.9 is classified as normal weight per WHO thresholds.
When to Use This Calculator
- Track personal health metrics over time alongside guidance from your clinician.
- Understand how lifestyle changes may influence a given health number.
- Compare values against recognized reference ranges from CDC, NIH, or WHO.
Limitations & Common Mistakes
- Not a substitute for medical advice. Always consult a qualified clinician for anything that affects your care.
- Population-level formulas don't account for individual medical history, medications, or body composition nuances.
- Reference ranges evolve, use current CDC/NIH/WHO values when accuracy matters.
Frequently Asked Questions
How does the BMI Calculator work?
Enter your weight (default: 170) and any other inputs; the calculator instantly applies its bmi formula and shows the result with details. All math runs in your browser; nothing is sent to a server.
Is the BMI Calculator accurate for body metrics decisions?
It uses standard, documented formulas that match published references. For high-stakes body metrics decisions, verify the result against an authoritative source (industry calculator, professional advisor, or government data). The calculator is a planning estimate, not a substitute for professional judgment.
What inputs does the BMI Calculator require?
3 inputs: Unit System, Weight, Height. Each has a sensible default; replace with your own values to get a result tailored to your situation.
Can I bookmark or share the BMI Calculator?
Yes — the URL is stable: https://www.calcintel.com/calculator/bmi. Inputs reset to defaults on each visit (no input is stored), so screenshot or copy the result if you want to preserve a specific scenario.
Related Calculators
More Health →BMR Calculator
Calculate your Basal Metabolic Rate, the calories your body burns at complete rest.
TDEE Calculator
Calculate your Total Daily Energy Expenditure, the total calories you burn each day including activity.
Calorie Intake Calculator
Calculate how many calories you should eat daily based on your goals, lose, maintain, or gain weight.
BMI Calculator for Children
Calculate BMI for children and teens (ages 2-20) using CDC growth charts and age-based percentiles.
Related guides
- TDEE: The Only Calorie Number That Actually Drives Weight ChangeBMR tells you the baseline. Calorie intake tells you the input. TDEE is the number that decides whether you lose, maintain, or gain, and it is the one most people miscalculate.
- BMI vs. Body Fat Percentage: Which Number Actually Measures HealthBMI is free and fast. Body fat percentage is more accurate. Waist-to-hip ratio predicts cardiovascular risk better than either. Here is when to use which, and what the CDC and WHO actually recommend.
Source: BLS Consumer Price Index, 2026.