BMI + Body Fat Percentage Calculator
Use this tool to calculate your Body Mass Index (BMI) and estimate your body fat percentage using your age and sex.
Body fat is estimated with a validated BMI-based formula for adults (not a diagnostic test).
What this calculator tells you
A standard BMI calculator only gives one number based on weight and height. That can be useful, but it does not directly tell you how much of your body is fat versus lean tissue. This calculator adds an estimated body fat percentage so you get a more practical view of body composition.
You will get:
- Your BMI value and BMI category.
- An estimated body fat percentage based on BMI, age, and sex.
- A body fat category to help interpret the number.
- A healthy weight range based on a BMI of 18.5 to 24.9.
BMI vs. body fat percentage
BMI is a screening tool
BMI (Body Mass Index) is a ratio of weight to height. It is widely used because it is quick and cost-free. It can identify population-level risk trends and is often used in clinics for an initial health screen.
Body fat percentage is more specific
Body fat percentage estimates how much of your total body weight is fat mass. That makes it more informative for people with higher muscle mass, older adults, or anyone who wants to track fat loss and not just total scale weight.
How the formula works
This page uses:
- BMI formula: weight/height² (with metric or imperial conversions).
- Estimated body fat formula (adults):
Men:1.20 × BMI + 0.23 × age − 16.2
Women:1.20 × BMI + 0.23 × age − 5.4
This method is practical and research-backed for large groups, but remember: it is still an estimate, not a direct measurement like DEXA or hydrostatic testing.
Interpreting your result
BMI categories
- Underweight: Below 18.5
- Normal weight: 18.5 to 24.9
- Overweight: 25.0 to 29.9
- Obesity: 30.0 and above
Body fat categories (general adult ranges)
Men
- Essential fat: 2–5%
- Athletes: 6–13%
- Fitness: 14–17%
- Average: 18–24%
- Obese: 25%+
Women
- Essential fat: 10–13%
- Athletes: 14–20%
- Fitness: 21–24%
- Average: 25–31%
- Obese: 32%+
Important limitations
- Not intended for children, pregnancy, or medical diagnosis.
- Very muscular individuals may be classified as overweight by BMI despite low fat.
- Hydration, ethnicity, age, and body shape can affect estimation accuracy.
- Use trends over time, not a single value, to guide decisions.
How to reduce body fat in a sustainable way
1) Focus on calorie balance
Create a modest calorie deficit (typically 250–500 kcal/day) instead of crash dieting.
2) Prioritize protein and resistance training
Protein helps preserve lean mass while lifting supports metabolism and body composition.
3) Walk more and sit less
Daily steps are a simple, repeatable way to increase energy expenditure.
4) Sleep and stress management
Poor sleep and high stress can increase hunger and slow progress.
Bottom line
A BMI calculator with body fat percentage gives a better snapshot than BMI alone. Use it as a guide, pair it with waist measurements and progress photos, and review changes over several weeks. If you have medical conditions or major weight-loss goals, talk to a licensed healthcare professional for a personalized plan.