function calculateBmiAndWeightLoss() {
var weightKg = parseFloat(document.getElementById("weightKg").value);
var heightCm = parseFloat(document.getElementById("heightCm").value);
var targetBmiInput = document.getElementById("targetBmi").value;
var targetBmi = parseFloat(targetBmiInput);
var currentBmiDisplay = document.getElementById("currentBmiDisplay");
var bmiCategoryDisplay = document.getElementById("bmiCategoryDisplay");
var healthyWeightRangeDisplay = document.getElementById("healthyWeightRangeDisplay");
var weightLossSuggestion = document.getElementById("weightLossSuggestion");
var targetWeightDisplay = document.getElementById("targetWeightDisplay");
currentBmiDisplay.innerHTML = "";
bmiCategoryDisplay.innerHTML = "";
healthyWeightRangeDisplay.innerHTML = "";
weightLossSuggestion.innerHTML = "";
targetWeightDisplay.innerHTML = "";
if (isNaN(weightKg) || isNaN(heightCm) || weightKg <= 0 || heightCm <= 0) {
currentBmiDisplay.innerHTML = "Please enter valid positive numbers for weight and height.";
return;
}
var heightM = heightCm / 100;
var currentBmi = weightKg / (heightM * heightM);
var bmiCategory = "";
var categoryColor = "";
if (currentBmi = 18.5 && currentBmi = 25 && currentBmi < 29.9) {
bmiCategory = "Overweight";
categoryColor = "#e6b800"; // Darker yellow/orange
} else {
bmiCategory = "Obese";
categoryColor = "red";
}
currentBmiDisplay.innerHTML = "Your Current BMI: " + currentBmi.toFixed(2) + "";
bmiCategoryDisplay.innerHTML = "BMI Category: " + bmiCategory + "";
var minHealthyWeight = 18.5 * (heightM * heightM);
var maxHealthyWeight = 24.9 * (heightM * heightM);
healthyWeightRangeDisplay.innerHTML = "A healthy weight range for your height is between " + minHealthyWeight.toFixed(1) + " kg and " + maxHealthyWeight.toFixed(1) + " kg.";
if (currentBmi >= 25) {
var weightToLose = weightKg – maxHealthyWeight;
weightLossSuggestion.innerHTML = "To reach a healthy BMI, you might aim to lose at least " + weightToLose.toFixed(1) + " kg.";
} else if (currentBmi < 18.5) {
var weightToGain = minHealthyWeight – weightKg;
weightLossSuggestion.innerHTML = "To reach a healthy BMI, you might aim to gain at least " + weightToGain.toFixed(1) + " kg.";
}
if (!isNaN(targetBmi) && targetBmi > 0) {
if (targetBmi 35) { // Reasonable range for target BMI
targetWeightDisplay.innerHTML = "Please enter a realistic target BMI (e.g., 18.5 to 24.9).";
} else {
var weightForTargetBmi = targetBmi * (heightM * heightM);
targetWeightDisplay.innerHTML = "To achieve a Target BMI of " + targetBmi.toFixed(1) + ", your weight should be approximately " + weightForTargetBmi.toFixed(1) + " kg.";
}
} else if (targetBmiInput.trim() !== "") {
targetWeightDisplay.innerHTML = "Please enter a valid number for Target BMI.";
}
}
Understanding Your BMI for Weight Loss
The Body Mass Index (BMI) is a widely used screening tool that helps assess whether a person has a healthy weight relative to their height. While it doesn't directly measure body fat, it's a simple and quick indicator that can help identify potential weight categories that may lead to health problems.
How BMI is Calculated
BMI is calculated using a straightforward formula:
BMI = weight (kg) / [height (m)]2
For example, if you weigh 70 kg and are 1.70 meters (170 cm) tall:
Height in meters: 170 cm / 100 = 1.70 m
Height squared: 1.70 m * 1.70 m = 2.89 m2
BMI: 70 kg / 2.89 m2 = 24.22
This calculator automatically converts your height from centimeters to meters for you.
BMI Categories
The standard BMI categories are:
Underweight: Less than 18.5
Normal weight: 18.5 – 24.9
Overweight: 25.0 – 29.9
Obese: 30.0 or greater
Using BMI for Weight Loss Goals
While BMI is a useful starting point, it's important to remember its limitations. It doesn't account for muscle mass, bone density, overall body composition, or fat distribution. For instance, a very muscular athlete might have a high BMI but very little body fat, while an older adult with low muscle mass might have a "normal" BMI but a high percentage of body fat.
However, for the general population, BMI can be a good indicator for setting weight loss goals. If your BMI falls into the "Overweight" or "Obese" categories, reducing your weight to bring your BMI into the "Normal weight" range (18.5-24.9) can significantly improve your health and reduce the risk of various chronic diseases like heart disease, type 2 diabetes, and certain cancers.
How This Calculator Helps
Our BMI & Weight Loss Goal Calculator provides:
Your Current BMI: A quick assessment of your current weight status.
BMI Category: Identifies if you are underweight, normal weight, overweight, or obese.
Healthy Weight Range: Shows the weight range considered healthy for your specific height.
Weight Loss Suggestion: If you are overweight or obese, it calculates how much weight you might need to lose to enter the healthy BMI range.
Target Weight for a Specific BMI: If you have a particular BMI goal in mind (e.g., aiming for a BMI of 22), the calculator will tell you the weight you need to achieve that goal.
Important Considerations
Always consult with a healthcare professional or a registered dietitian before making significant changes to your diet or exercise routine. They can provide personalized advice based on your individual health status, medical history, and specific body composition, offering a more comprehensive assessment than BMI alone.
This calculator is a tool for informational purposes and should not replace professional medical advice.