Calculating your potential weight loss involves understanding the fundamental principle:
a calorie deficit. To lose weight, you must consistently consume fewer calories than your body
burns. This calculator helps you estimate the time it will take to reach your goal weight
based on your current weight, goal weight, and a targeted weekly calorie deficit.
The Science Behind It:
One kilogram of body fat is equivalent to approximately 7,700 kilocalories (kcal).
Therefore, to lose 1 kg, you need to create a deficit of 7,700 kcal.
This calculator uses this principle to project your weight loss timeline.
How the Calculator Works:
Current Weight: Your starting body weight in kilograms.
Goal Weight: Your desired body weight in kilograms.
Target Weekly Calorie Deficit: The average number of calories you aim to consume less than you burn each week. This can be achieved through a combination of diet and exercise. A common and sustainable deficit is between 500 to 1000 kcal per day, which translates to 3500 to 7000 kcal per week.
Calculations Performed:
Total Weight to Lose: Calculated as Current Weight - Goal Weight.
Total Calorie Deficit Needed: Calculated as Total Weight to Lose (kg) * 7700 kcal/kg.
Estimated Weeks to Reach Goal: Calculated as Total Calorie Deficit Needed / Target Weekly Calorie Deficit.
Example:
If you currently weigh 75 kg, your goal weight is 68 kg, and you aim for a weekly calorie deficit of 500 kcal:
Total Weight to Lose: 75 kg – 68 kg = 7 kg
Total Calorie Deficit Needed: 7 kg * 7700 kcal/kg = 53,900 kcal
This means it would take approximately 107.8 weeks to reach your goal weight under these conditions.
Important Considerations:
This is an estimation tool. Actual weight loss can vary significantly due to factors such as metabolism, muscle mass, hormonal changes, adherence to the deficit, and the accuracy of calorie tracking. It's always recommended to consult with a healthcare professional or a registered dietitian before starting any new weight loss program.
function calculateWeightLoss() {
var currentWeight = parseFloat(document.getElementById("currentWeight").value);
var goalWeight = parseFloat(document.getElementById("goalWeight").value);
var weeklyDeficit = parseFloat(document.getElementById("weeklyDeficit").value);
var resultDiv = document.getElementById("result");
resultDiv.innerHTML = ""; // Clear previous results
// Input validation
if (isNaN(currentWeight) || currentWeight <= 0 ||
isNaN(goalWeight) || goalWeight <= 0 ||
isNaN(weeklyDeficit) || weeklyDeficit <= 0) {
resultDiv.innerHTML = "Please enter valid positive numbers for all fields.";
return;
}
if (currentWeight <= goalWeight) {
resultDiv.innerHTML = "Your goal weight must be less than your current weight.";
return;
}
var weightToLose = currentWeight – goalWeight;
var totalKcalNeeded = weightToLose * 7700;
var estimatedWeeks = totalKcalNeeded / weeklyDeficit;
// Format the output
var formattedWeeks = estimatedWeeks.toFixed(1);
resultDiv.innerHTML = "Estimated weeks to reach goal: " + formattedWeeks + " weeks";
}