BMI Calculator
Calculate your Body Mass Index and find out what it means for your goals.
Please fill in all fields with valid values.
Underweight
<18.5
Normal
18.5–24.9
Overweight
25–29.9
Obese
30+

What is BMI?

Your Body Mass Index (BMI) is a simple calculation that divides your weight by the square of your height. The result places you into one of four categories: Underweight, Normal Weight, Overweight, or Obese.

BMI was developed as a population-level screening tool and is used by doctors, nutritionists, and fitness professionals worldwide as a quick reference point. While it is not a perfect measure of health or body composition, it gives you a useful starting point to set realistic goals.

The four BMI categories are:
  • Underweight: BMI below 18.5 — may indicate insufficient muscle or fat mass
  • Normal Weight: BMI 18.5–24.9 — associated with the lowest health risks for most adults
  • Overweight: BMI 25–29.9 — increased risk of metabolic and cardiovascular conditions
  • Obese: BMI 30 and above — significantly elevated health risks, fat loss is the top priority

BMI by Goal

Fat Loss

If your BMI is in the Overweight or Obese range, losing body fat is the most impactful thing you can do for your long-term health. A sustainable calorie deficit of 300–500 kcal per day combined with resistance training will help you lose fat while preserving muscle mass. Aim for 0.5–1% of body weight lost per week for best results.
  • Aggressive cut (500+ kcal deficit): Faster results but higher risk of muscle loss — not recommended without high protein intake
  • Moderate cut (300–500 kcal deficit): The sweet spot for most people — steady fat loss with minimal muscle loss
  • Slow cut (200–300 kcal deficit): Best for those close to their goal weight or highly active individuals

Maintenance

If your BMI falls in the Normal Weight range, your focus should be on maintaining your current weight while improving body composition over time. This means eating at roughly your TDEE, training consistently, and monitoring your weight monthly rather than daily. Use our TDEE Calculator to find your maintenance calories.

Muscle Gain

If your BMI is in the Normal or Underweight range and your goal is to build muscle, a slight calorie surplus of 200–300 kcal above your TDEE is ideal. Prioritize progressive resistance training and hit your daily protein target.
  • Lean bulk (200–300 kcal surplus): Slow but clean muscle gain with minimal fat gain
  • Standard bulk (300–400 kcal surplus): Slightly faster results, small amount of fat gain expected
  • Dirty bulk (500+ kcal surplus): Not recommended — excessive fat gain with no additional muscle benefit

BMI Limitations

BMI is a useful screening tool but has real limitations you should be aware of:
  • Does not distinguish muscle from fat: A muscular athlete can have a high BMI without carrying excess body fat
  • Does not account for fat distribution: Where you carry fat matters — abdominal fat carries more health risk than fat stored elsewhere
  • Varies by age and ethnicity: Asian populations may face health risks at lower BMI thresholds than standard classifications suggest
  • Not reliable for the elderly: Older adults often lose muscle mass, which can result in a normal BMI despite unhealthy body composition
Use BMI as a starting point, not a definitive measure of your health. For a fuller picture, consider tracking body fat percentage and waist circumference alongside your BMI.

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BMI Calculator FAQ

What is a healthy BMI?
A BMI between 18.5 and 24.9 is considered healthy for most adults. However, healthy BMI ranges can vary slightly by age and ethnicity. Asian populations, for example, may have health risks at lower BMI thresholds than the standard classification suggests.
No — BMI is not accurate for highly muscular individuals. Since muscle is denser than fat, athletes and bodybuilders often show a high BMI despite having low body fat. In these cases, body fat percentage is a more reliable measure.
Yes. This is called normal weight obesity and occurs when someone has a healthy BMI but a high percentage of body fat due to low muscle mass. This is why BMI should always be considered alongside other measures like waist circumference and body composition.
Once every 4–8 weeks is sufficient for most people. BMI changes slowly and daily fluctuations in water weight can give misleading readings. Track trends over months rather than obsessing over weekly numbers.
The BMI formula is the same for men and women, but body fat distribution differs between sexes. Women naturally carry more body fat than men at the same BMI. Some health professionals use gender-specific adjustments when interpreting BMI results.
Start with sustainable changes — a modest calorie deficit, daily walking, and resistance training 2–3 times per week. Even a 5–10% reduction in body weight produces significant health benefits. Use our TDEE Calculator to find your calorie target and our Protein Calculator to protect muscle while losing fat.
Last updated: April 2026