Body Mass Index (BMI) is a quick, inexpensive screening tool for measuring weight category (underweight, normal, overweight, or obese). While it doesn't measure body fat directly, it is globally adopted by healthcare professionals as a first-step assessment. Ensuring your BMI calculation is accurate relies on a precise formula and correct input units.
The Standard BMI Formula
Our BMI calculator uses the universally accepted metric formula. The calculation is based on your weight in kilograms (kg) divided by the square of your height in meters (m):
BMI = Weight (kg) / [Height (m)]²
Our PHP script ensures the calculation is done correctly using basic arithmetic operators, providing a precise result to two decimal places.
Calculation in PHP
The simplicity of the formula allows for extremely fast execution using native PHP. The core calculation requires only multiplication and division:
$bmi = $weight_kg / ($height_m * $height_m);
$bmi_rounded = number_format($bmi, 2);
Interpreting Your BMI Result
After calculating the BMI score, our PHP script uses conditional logic (`if/elseif/else`) to instantly classify your result according to standard international guidelines:
- **Underweight:** BMI below 18.5
- **Normal Weight:** BMI between 18.5 and 24.9
- **Overweight:** BMI between 25.0 and 29.9
- **Obese:** BMI 30.0 or higher
Accurate Input is Essential
The most common error in BMI calculation is using the wrong units. Our calculator standardizes input to **kilograms (kg)** and **meters (m)**. If you typically measure your height in feet/inches or weight in pounds (lb), you must convert those values first (which you can do using our Unit Converter!).
Conclusion and Next Steps
Our BMI calculator provides a quick, accurate screening tool for weight category, powered by robust PHP logic. We maintain strict adherence to the correct formula and precise metric inputs. Use the tool regularly to monitor your progress, and remember to always consult a healthcare professional for personalized health advice.