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Enter your height and weight, then click Calculate// calculate bmi and healthy weight range instantly
Calculate your Body Mass Index (BMI) instantly. Enter height and weight in metric or imperial units to get your BMI score with healthy range indicator and category.
Ready to calculate
Enter your height and weight, then click CalculateSelect Metric (kg/cm) or Imperial (lb/ft/in) depending on your preference.
Input your height and weight. Age and sex are optional for context notes.
Click Calculate to instantly see your BMI score, category, and healthy weight range.
The BMI Calculator computes your Body Mass Index — a numerical value derived from height and weight used to classify weight status. Results include your BMI score, category (Underweight, Normal, Overweight, Obese), healthy weight range, and ideal weight midpoint.
BMI (Body Mass Index) is calculated by dividing your weight in kilograms by the square of your height in meters: BMI = kg/m². In imperial units: BMI = (lb / in²) × 703. It provides a simple numeric measure of body fatness based on height and weight.
The standard WHO BMI categories are: Underweight (below 18.5), Normal weight (18.5–24.9), Overweight (25.0–29.9), Obese Class I (30.0–34.9), Obese Class II (35.0–39.9), and Obese Class III (40.0 and above).
BMI is a general screening tool and has limitations. It doesn't account for muscle mass, bone density, fat distribution, age, sex, or ethnicity. Athletes may have high BMI due to muscle rather than fat. It's a useful starting point but shouldn't replace professional medical assessment.
For most adults, a healthy BMI range is 18.5 to 24.9. For adults over 65, a slightly higher BMI (22–27) may actually be protective. Children and teens use age- and sex-specific BMI percentile charts rather than adult BMI cutoffs.
BMI Prime is the ratio of your actual BMI to the upper limit of the normal BMI range (25.0). A BMI Prime of 1.0 means your BMI is exactly 25. Values below 1.0 indicate normal or underweight; above 1.0 indicates overweight or obese. It lets you quickly see how far you are from the normal range.
Ideal weight is derived from the normal BMI range (18.5–24.9) applied to your height. The midpoint of this range (BMI ≈ 21.75) gives the ideal weight midpoint shown in results. Multiply the ideal BMI by your height in meters squared: ideal weight (kg) = BMI × height(m)².
A BMI Calculator is a simple online tool that computes your Body Mass Index — a numerical value derived from your height and weight that serves as a broad indicator of body fatness. The BMI formula is straightforward: divide your weight in kilograms by the square of your height in meters. The resulting number places you into one of several weight categories recognized by health organizations worldwide.
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The standard BMI formula uses metric units: BMI = weight(kg) / height(m)². For example, if you weigh 70 kg and are 1.75 m tall, your BMI = 70 / (1.75 × 1.75) = 70 / 3.0625 ≈ 22.9. In imperial units, the formula adjusts to: BMI = (weight(lb) × 703) / height(in)². Our calculator handles both unit systems automatically, so you simply enter your measurements and get your result instantly.
The World Health Organization (WHO) defines four primary BMI categories for adults:
Rather than aiming for a single "ideal" number, our BMI calculator shows you a healthy weight range based on the normal BMI category (18.5–24.9) applied to your specific height. This range tells you the span of weights that would put you in the normal BMI category. The midpoint of this range — calculated using a BMI of approximately 21.75 — provides a useful ideal weight target. For someone 175 cm tall, the healthy weight range is approximately 56.6 to 76.3 kg, with an ideal midpoint around 66.5 kg.
BMI Prime is a simple dimensionless number that expresses your BMI relative to the upper threshold of the normal range (25.0). The formula is: BMI Prime = BMI / 25. A value of exactly 1.0 means your BMI is 25 — right at the border between normal and overweight. Values below 1.0 mean you're in the normal or underweight range; values above 1.0 indicate overweight or obese. BMI Prime makes it easy to quickly gauge how far you are from the healthy range boundary in relative terms.
While BMI is a widely used and convenient screening tool, it has important limitations that both users and healthcare providers recognize:
For these reasons, BMI is best used as one data point among several, alongside waist circumference measurements, blood pressure, cholesterol levels, and consultation with healthcare professionals.
For individuals under 20 years old, standard adult BMI categories do not apply. Children and teens are assessed using age- and sex-specific BMI-for-age percentile charts. A BMI at or above the 85th percentile is considered overweight, and at or above the 95th percentile is considered obese. Our calculator includes age and sex inputs for contextual notes, but for anyone under 18, we recommend consulting a pediatric growth chart or healthcare provider for accurate assessment.
If your BMI falls outside the healthy range, sustainable lifestyle changes are the most effective approach. For those looking to lower their BMI: focus on a balanced diet with appropriate caloric intake, increase physical activity with both cardio and strength training, ensure adequate sleep (poor sleep is linked to weight gain), and manage stress levels. For those looking to increase their BMI from underweight: work with a healthcare provider or registered dietitian to ensure nutritional needs are met safely. Remember that weight changes of 0.5–1 kg per week are generally considered healthy and sustainable.
While the BMI formula is simple, our online calculator adds several layers of value: automatic unit conversion between metric and imperial, instant visual representation on the BMI scale, calculation of your healthy weight range specific to your height, BMI Prime calculation, and clear category classification with health context. All calculations happen entirely in your browser — no data is sent to any server, preserving your privacy completely.