How to calculate BMI with this BMI Calculator
Use Height and Weight as the two inputs. Choose the unit beside each value, then click Calculate BMI. The result converts imperial entries to metric, shows the formula and intermediate values, and assigns a Weight category from the unrounded BMI before displaying the BMI to one decimal place.
- Enter a positive number in Height and choose
cm,ft, orin. - Enter a positive number in Weight and choose
kgorlb. - Click Calculate BMI to display the BMI, weight category, conversions, assumptions, and formula.
- Click Copy result or Download result (.txt) to keep the plain-text result, or click Reset to clear the fields.
What BMI Calculator shows for height and weight
The result shows the BMI to one decimal place, the matching Weight category, the values as entered, and the metric height and weight used in the calculation. For example, 175 cm and 70 kg produce this result:
Height: 175.0 cm
Weight: 70.0 kg
BMI: 22.9
Weight category: Normal weightThe formula is BMI = weight (kg) / height (m)^2. If you choose ft or in, the calculator converts Height to centimetres first. A lb value is converted with 1 lb = 0.45359237 kg; one inch is 2.54 cm and one foot is 30.48 cm.
The category uses the full calculated value, even though the displayed BMI is rounded to one decimal place. The thresholds are Underweight below 18.5, Normal weight below 25, Overweight below 30, and Obese at 30 or above.
What happens when BMI input is invalid
Calculation stops when Height or Weight is missing, zero, negative, or invalid. An error message appears, and Result stays hidden. Height and Weight units determine how valid numbers are converted.
Editing Height or Weight, or changing a unit, hides the current result. Click Calculate BMI again after the change. Reset clears both values, restores cm and kg, and hides the result.
Copy or download a BMI result
Click Copy result for a plain-text summary. If clipboard copying fails, the result text remains available for manual selection. Click Download result (.txt) to save that same summary as a text file. It includes the entered and metric values, BMI, category, and a not-medical-advice note; it does not include the formula or threshold table.
Choose units for a BMI calculation
Keep cm and kg selected for metric measurements. For height in feet or inches and weight in pounds, choose ft or in for Height and lb for Weight. The result lists the metric conversions used before the BMI formula is applied.
After a calculation, Copy result keeps the plain-text summary available for copying, and Download result (.txt) creates a text file named bmi-calculator-result.txt. Reset clears the previous pair before you enter another one.
When to use another health calculator
Open the health calculators category when the needed input is age or calorie-related data rather than height and weight. Body Fat Percentage Calculator uses height, neck, waist, and, for women, hip measurements. Calorie Calculator estimates BMR, maintenance calories, and a daily target from activity and other inputs. Age Calculator calculates elapsed age from a date of birth to a target date.
The BMI calculation runs in browser-side JavaScript, and this calculator script does not send the Height or Weight values to a server. That statement applies to these calculator inputs, not to every request made by other page components.
Frequently asked questions
How do I calculate BMI from height and weight?
BMI is calculated as weight in kilograms divided by height in meters squared (BMI = kg / m^2). If you enter imperial units, height and weight are first converted to metric before applying the same formula.
What category does my BMI result use?
The calculator labels a BMI below 18.5 Underweight, 18.5 or above and below 25 Normal weight, 25 or above and below 30 Overweight, and 30 or above Obese. The category is based on the unrounded calculation.
Can BMI Calculator use feet, inches, and pounds?
Yes. Choose ft or in beside Height and lb beside Weight. The calculator converts those entries to metric before applying the BMI formula and shows the converted values.
Why is my BMI result hidden after I edit a value?
Editing Height, Weight, or a unit hides the current result. Click Calculate BMI again after making the change.