BMI Calculator
Use our free BMI Calculator to check your Body Mass Index, understand healthy weight ranges, and get practical next steps for fitness and weight goals.
Body Mass Index (BMI) is a simple numerical measure that uses your weight and height to estimate body fat for most adults. BMI is calculated using the formula: BMI = weight (kg) ÷ height (m²). Clinicians and public health organizations use BMI to screen for weight categories that may lead to health problems, such as high blood pressure, diabetes, and cardiovascular disease.What is BMI?
How to calculate your BMI
To compute BMI manually: measure your weight in kilograms and your height in metres, square your height, then divide weight by the squared height. For example, if you weigh 70 kg and are 1.75 m tall: 70 ÷ (1.75 × 1.75) = 22.86. That value falls in the “healthy” range.
BMI Categories (adult)
The World Health Organization (WHO) categories commonly adopted are:
- Underweight: BMI < 18.5
- Normal weight: BMI 18.5 – 24.9
- Overweight: BMI 25 – 29.9
- Obesity: BMI > 30
These bands are useful for population screening — but individual health depends on many factors including muscle mass, bone structure, and fat distribution.
Benefits and limitations of BMI
Benefits: BMI is fast, inexpensive, and widely used for population-level risk assessment. It helps guide public health policy and raises awareness around weight-related health risks.
Limitations: BMI does not distinguish muscle from fat. Athletes with high muscle mass may have an elevated BMI but low body fat. Older adults may have normal BMI but high body fat with low muscle mass. For nuanced assessment, use our Body Fat Calculator or Lean Body Mass Calculator.
What to do with your BMI result
If your BMI is outside the healthy range, consider these steps:
- Consult a healthcare professional for personalized assessment.
- Track diet and physical activity — try our Calorie Calculator and TDEE Calculator.
- For performance or aesthetic goals, pair BMI with body composition tools such as body fat percentage and waist circumference.
Frequently Asked Questions
What is a good BMI for my age?
A good BMI depends on your age and overall health, but generally the healthy range of 18.5–24.9 applies to most adults. For seniors, doctors may consider slightly higher BMIs acceptable.
What is the average BMI for a 70 year old?
The average BMI for a 70 year old is often slightly higher than younger adults, with many falling in the 23–28 range. Maintaining a BMI around 23–27 is considered healthy for seniors.
What is the ideal weight according to height and age?
Ideal weight is calculated using BMI and height. While age doesn’t change the BMI formula, older adults may be advised to maintain a slightly higher BMI for health and strength.
Is BMI calculated differently for seniors?
No, BMI is calculated the same way for all adults, but the interpretation may vary. Seniors may be considered healthy at slightly higher BMI ranges.
What BMI is considered stocky?
A BMI between 25–29.9 (overweight category) may be considered stocky, especially if muscle mass is high.
What size is BMI 23?
A BMI of 23 is typically a medium build and corresponds to a healthy weight for most heights.
What BMI to qualify for Wegovy?
To qualify for Wegovy, you usually need a BMI of 30 or greater, or 27 or greater with weight-related health issues.
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