BMI Calculator: Score, Range, and Target Weight

Is your weight in proportion to your height? Body mass index, or BMI, is one quick way to check. The BMI Calculator turns height and weight into a single score and shows where it falls on the adult scale.

It is built for adults aged 18 and older who want a simple screening number. It also shows a weight range for your height. You get a target weight and the gap to it as well.

Table of Contents

• What the BMI Calculator Does
• How to Use It, Step by Step
• The BMI Formula
• Worked Examples
• How to Read the Results
• What BMI Can and Cannot Tell You
• Limitations and Assumptions
• FAQs About the BMI Calculator

What the BMI Calculator Does

The tool works in metric or imperial units. It updates as you type, so there is no calculate button. These are the main outputs.

• BMI Score: your result with one decimal, plus a category label.
• Healthy Weight Range: the weights that match a BMI of 18.5 up to under 25.0 at your height.
• Weight Adjustment: how much to gain or reduce to reach that range, or "On target". It uses your chosen unit.
• Target Weight, Range Midpoint, and Weight Difference: cards based on the Target BMI you choose.
• Position on a 0 to 40 BMI Scale: your BMI divided by 40, shown as a bar. Short written insights follow.
• Buttons for Copy result, Export CSV, Print, and Reset.

How to Use It, Step by Step

1. Pick the Metric or Imperial tab. Your numbers convert when you switch.
2. In Metric, enter Height (cm) from 80 to 250 and Weight (kg) from 20 to 350.
3. In Imperial, enter Height (feet) from 2 to 8 and Height (inches) from 0 to 11.9. Then enter Weight (lb) from 44 to 770.
4. Enter your Age (years, adults 18 and older) as a whole number from 18 to 120.
5. Set the Target BMI between 18.5 and 24.9. The sample value is 22.
6. Read the cards. If a field is blank or out of range, the cards show "N/A" and a message names the problem.

The BMI Formula

BMI divides your weight in kilograms by your height in meters, squared. In Imperial mode, the tool first converts pounds to kilograms and inches to meters. The weights for the healthy range come from the same formula run backward.

• Healthy range low end = 18.5 × height in meters squared.
• Healthy range high end = 25.0 × height in meters squared.
• Range midpoint = 21.75 × height in meters squared.
• Target weight = Target BMI × height in meters squared.
• Pounds convert at 2.2046226218 per kilogram, and inches at 0.0254 meters each.

Worked Examples

Daniel is 180 cm tall and weighs 82 kg. He keeps the Target BMI at 22. The height in meters squared is 1.8 × 1.8, or 3.24.

Priya uses the Imperial tab at 5 ft 9 in and 185 lb, with the same target. Her BMI is 27.3. Her healthy range is 125.3 to 169.3 lb, and her target weight is 149.0 lb. Her adjustment reads 15.7 lb to reduce.

How to Read the Results

The category follows standard adult cutoffs. Below 18.5 is Underweight. From 18.5 to under 25 is Healthy. From 25 to under 30 is Overweight, and 30 or more is Obesity.

Weight Adjustment compares you with the range, not with your target. Weight Difference compares you with your target weight. So a person can be inside the range and still show a gap to the target.

The scale card is only your BMI divided by 40, capped at 100%. It is not a population percentile. The insight list adds a note for adults 65 and older, and a note about muscle for everyone else.

What BMI Can and Cannot Tell You

BMI uses only height and weight. It cannot tell muscle from fat, or show where fat sits on the body. A strong athlete and a person with little muscle can share the same score.

That is why BMI works best as a first screen. Pair it with a waist measure, such as the Waist to Hip Ratio Calculator. You can also estimate fat share with the Body Fat Percentage Calculator.

Two other tools give a second view of the same height. The Healthy Weight Range Calculator shows the BMI range alongside two classic formulas. The Ideal Weight Calculator offers another way to compare.

Frame matters too. A person with a large frame may sit near the top of the range. The Body Frame Size Calculator can help you judge that. If you plan to change your weight, the Calorie Calculator estimates daily energy needs.

For more checks on fitness and body numbers, browse the Health and Fitness tools hub.

Limitations and Assumptions

• The tool is for adults. It rejects ages under 18 because children and teens need BMI-for-age growth charts.
• The Target BMI field only accepts 18.5 to 24.9, so you cannot set a target outside the healthy band.
• Results are screening estimates, not a diagnosis. Pregnancy, illness, and heavy training can all change what a score means.
• In Imperial mode, the total height must still fall between 80 and 250 cm, the same limits as Metric.
• Up to 8 results are saved in a history table in your own browser. A row is saved when you press Enter, leave a field, or use Copy or Export.
• The Print button prints the whole page, not only the result.

Please do not use this result to start a crash diet. People with an eating disorder, or a medical condition, should talk with a doctor first. A doctor or dietitian should guide any major weight change.

FAQs About the BMI Calculator

This calculator gives general estimates only and is not medical advice. Reviewed for general accuracy by Prof. Dr. Khalil Mudassar, PhD.