BMI Calculator
Calculate your Body Mass Index and see which weight category it falls into.
The BMI calculator measures whether your weight is in a healthy range for your height. BMI, or Body Mass Index, is used worldwide as a quick screening tool, although it does not distinguish between muscle and fat — athletes can have a high BMI while being very fit.
How to use the calculator
- Enter your weight in kilograms.
- Enter your height in centimetres.
- The calculator shows your BMI and the standard category.
- It also shows the healthy weight range for your height.
How it is calculated
Healthy range = BMI 18.5 to 24.9, so healthy weight = 18.5 × height2 to 24.9 × height2.
Worked example
70 kg at 170 cm
Height in metres = 1.70, so BMI = 70 ÷ 2.89 ≈ 24.2
Healthy weight range for this height is about 53.5 kg to 72 kg.
Who should use this calculator
- Adults checking whether their weight sits in a healthy range for their height, as a starting point rather than a verdict.
- Anyone beginning a fitness or diet plan and wanting a baseline number to track over the coming months.
- People whose doctor has flagged weight as a risk factor and who want to understand what BMI actually measures.
- Anyone who has been told they are overweight but whose weight has been stable for years, and wants context before making changes.
Common mistakes to avoid
- Using BMI on muscular people. Muscle is denser than fat, so athletes and regular weight-trainers often score as overweight while carrying very little fat. Waist measurement and body fat percentage tell a fairer story.
- Ignoring where the fat sits. Two people with the same BMI can have very different risks. Fat around the abdomen is more strongly linked to metabolic problems than fat on the hips and thighs, which is why waist circumference matters alongside BMI.
- Applying adult BMI to children. Children and teenagers need age and sex specific growth charts, not the adult scale. Pregnancy also invalidates the calculation.
- Weighing yourself daily and reacting to it. Weight moves with water, salt, hormones and food in the gut. Weekly averages taken at the same time of day show the real trend.
- Treating BMI as a diagnosis. It is a screening tool. A high BMI is a prompt for a fuller assessment, not a medical conclusion.
What BMI does not measure
BMI compares weight with height and nothing else. It cannot tell whether the weight is muscle, fat, bone or water, and it says nothing about where fat is stored or how fit you are. Someone at 24.2 — the result for 70 kg at 170 cm — could be a lean runner or someone with very little muscle and a high fat percentage.
Indian and wider Asian populations tend to develop health risks at a lower BMI than the standard scale suggests, which is why many clinicians here treat 23 as the upper end of healthy rather than 25. If your BMI sits between 23 and 27, pair it with a waist measurement: over 90 cm for men and 80 cm for women is a signal worth discussing with a doctor regardless of what the BMI number says.
BMI terms explained
- BMI
- Body Mass Index — weight in kilograms divided by height in metres squared.
- Waist circumference
- A tape measurement around the navel. It captures abdominal fat, which BMI misses entirely.
- Body composition
- The split between fat mass and lean mass. Two people at the same weight can have very different compositions.
- Healthy range
- For most adults, a BMI of 18.5 to 24.9. Indian guidance often treats 23 and above as a warning level.
- Screening tool
- A quick first-pass indicator that suggests whether further assessment is useful, not a diagnosis on its own.
When to ignore the BMI number
There are several situations where BMI tells you nothing useful: during pregnancy, for children and teenagers, for anyone with a lot of muscle, and for people over 70, where a slightly higher weight is often protective. Illness, recent surgery and medication can also shift body water enough to change the figure within days. In all of those cases, waist circumference, body fat percentage, strength and how clothes fit are far better guides. Use BMI as one input, never as the verdict.
Frequently asked questions
What is a healthy BMI?
For adults, a BMI between 18.5 and 24.9 is considered healthy. Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 or above is obese. Indian guidelines suggest 23 as the upper limit of healthy, because health risks rise earlier.
Is BMI accurate for everyone?
BMI is a screening tool, not a diagnosis. It can mislead for athletes with high muscle mass, pregnant women, children and the elderly. Waist circumference and body fat percentage give a fuller picture.
How can I improve my BMI?
If your BMI is high, a combination of portion control, regular activity (150 minutes a week), strength training and adequate sleep works better than crash diets. If it is low, add nutrient-dense calories and protein gradually.