BMI Calculator (Metric: kg & cm)
Enter your weight in kilograms and height in centimeters to calculate your Body Mass Index instantly.
What is BMI?
BMI (Body Mass Index) is a quick screening number that compares your weight to your height. It helps estimate whether your body weight is in a range that is generally considered underweight, normal, overweight, or obese.
BMI does not directly measure body fat, but it is widely used by doctors, trainers, and public health organizations as a first-level health indicator.
BMI Formula in kg
The metric BMI formula is simple:
BMI = weight (kg) / [height (m)]²
If your height is entered in centimeters, divide by 100 first to convert it to meters. Example:
- Weight = 70 kg
- Height = 170 cm = 1.70 m
- BMI = 70 / (1.70 × 1.70) = 24.22
BMI Categories (Adults)
| BMI Range | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Normal weight |
| 25.0 – 29.9 | Overweight |
| 30.0 – 34.9 | Obesity Class I |
| 35.0 – 39.9 | Obesity Class II |
| 40.0 and above | Obesity Class III |
How to use this BMI calculator in kg
Step-by-step
- Enter your weight in kilograms.
- Enter your height in centimeters.
- Click Calculate BMI.
- Read your BMI value, category, and healthy weight range.
Healthy weight range from your height
This calculator also estimates a healthy body weight range based on a BMI of 18.5 to 24.9. This can give you a practical target range in kilograms for your current height.
Important limitations of BMI
BMI is useful, but it does have limits. It may not be accurate for everyone.
- Muscular people may show high BMI with low body fat.
- Older adults may have normal BMI but low muscle mass.
- Children and teens need age- and sex-specific BMI percentiles.
- Pregnancy changes body composition, so BMI is less useful during this period.
Tips to improve your BMI over time
If your BMI is high
- Create a small calorie deficit (consistent, not extreme).
- Prioritize protein, vegetables, and high-fiber foods.
- Walk daily and include strength training 2–4 times per week.
- Reduce sugary drinks and ultra-processed snacks.
- Track progress weekly, not just daily.
If your BMI is low
- Increase calories gradually with nutrient-dense foods.
- Eat protein-rich meals and snacks throughout the day.
- Use resistance training to build lean muscle.
- Sleep 7–9 hours for better recovery and appetite regulation.
Frequently asked questions
Is BMI accurate?
It is accurate as a population-level screening method, but less precise for specific individuals with unusual body composition (very high muscle or low muscle mass).
Should I use BMI alone?
No. Combine BMI with waist circumference, blood markers, fitness level, and medical history for a more complete health picture.
What is a good BMI?
For most adults, a BMI from 18.5 to 24.9 is considered the normal range. But individual goals may differ based on age, health conditions, and activity level.