Free Online BMI Calculator
Calculate your Body Mass Index (BMI) in metric or imperial units and see where you fall on the WHO category scale. Also shows the ideal weight range for your height and how far you are from the normal range.
Ideal weight for your height
BMI Categories (WHO standard)
BMI is a rough screening tool and does not account for muscle mass, bone density, or body composition. Consult a healthcare provider for a complete assessment.
Try this example
You are 175 cm tall and weigh 78 kg. You want to know your BMI and whether that is in the healthy range.
- 1Pick Metric units.
- 2Enter 175 in the height field and 78 in the weight field.
- 3Read the BMI and category. The ideal weight range section tells you the kg range that would land you in normal BMI.
What BMI measures, simply
Body Mass Index is weight divided by height squared. Metric formula: BMI = weight(kg) / height(m)^2. Imperial: BMI = (weight(lb) / height(in)^2) × 703. The result is a single number that places you in one of four categories defined by the World Health Organization.
Under 18.5 is underweight. 18.5 to 24.9 is the normal range. 25 to 29.9 is overweight. 30 and above is obese, with further subcategories above that. These ranges apply to most adults worldwide, with regional adjustments for some Asian populations who show elevated cardiovascular risk at lower BMIs.
What BMI does well and what it misses
BMI is a good population-level screening tool. If you compare a million people with BMI over 30 to a million people with BMI between 20 and 24, the first group has measurably higher rates of diabetes, heart disease, and several cancers. That statistical relationship is strong enough that BMI has been used for decades in public health research.
BMI misses several things about individuals. It cannot tell muscle from fat, so a muscular athlete can score "overweight" while being in excellent health. It cannot tell fat location, so two people with the same BMI but different fat distributions have different health risks (abdominal fat is more dangerous than subcutaneous fat). It does not adjust for age, which affects muscle mass, or for frame size.
Use BMI as a starting conversation, not a diagnosis. Combined with a waist measurement and a basic blood panel, it becomes much more informative. For a deeper look at what BMI tells you and what it misses, see our [guide to BMI](/blog/bmi-calculator-what-it-tells-you-and-what-it-misses).
Why we show an ideal weight range instead of a single number
Many BMI calculators tell you the single weight that produces a BMI of 22 (the middle of the normal range) and call that your "ideal weight". That is misleading. BMI is a range, not a point. Any weight between BMI 18.5 and 24.9 is statistically normal.
We show the full kg (or lb) range for your height, so you know you are in the normal zone if your weight falls anywhere inside it. If you are below the range, the tool estimates how much you would need to gain to reach normal. If you are above, it estimates how much to lose.
These are rough estimates. Real weight management depends on body composition, activity level, age, and many other factors. Use the numbers as a reference, not as a goal to hit precisely.
Privacy note
This calculator runs entirely in your browser. Your height and weight are not sent to any server, not stored in cookies, not used in any analytics. Open your browser developer tools, switch to the Network tab, and enter your numbers. You will see zero outbound requests. The calculation is pure arithmetic and takes less than a millisecond.
How to Use
- 01Choose metric (cm/kg) or imperial (ft-in/lb) units.
- 02Enter your height and weight.
- 03See your BMI, category, and how it compares to the ideal range for your height.
FAQ
What is the ideal weight range?▼
The weight that would put your BMI between 18.5 and 24.9 (the WHO normal range) given your height. This is a statistical average and may not suit athletes, the elderly, or specific body compositions.
What is a healthy BMI?▼
WHO considers 18.5 to 24.9 normal for adults. Below is underweight, 25 to 29.9 is overweight, 30+ is obese.
Is BMI reliable?▼
BMI is a screening tool, not a diagnosis. It does not account for muscle mass, bone density, age, sex, or fat distribution. Talk to a healthcare provider for a complete assessment.