This is the difference between calories burned and calories consumed per week.
Estimated Time to Reach Target Weight:
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Understanding Weight Loss Calculations
Losing weight is a common health goal, and understanding the time it might take can be a powerful motivator. This calculator helps estimate how long it will take to reach your target weight based on your current weight, desired weight, and your projected weekly calorie deficit.
The fundamental principle behind weight loss is creating a calorie deficit. This means consistently consuming fewer calories than your body burns. On average, it's estimated that a deficit of 3,500 calories is required to lose one pound (approximately 0.45 kg) of body fat. For metric users, this translates to roughly a 7,700 calorie deficit to lose one kilogram.
How the Calculator Works:
Total Weight to Lose: Calculated by subtracting your target weight from your current weight (in kg).
Total Calorie Deficit Needed: Multiply the total weight to lose (in kg) by 7,700 kcal/kg to find the total calorie deficit required.
Estimated Weeks: Divide the total calorie deficit needed by your planned weekly calorie deficit.
Formula Used:
Total Weight Loss (kg) = Current Weight (kg) – Target Weight (kg)
Total Calorie Deficit Needed (kcal) = Total Weight Loss (kg) * 7700
Estimated Time (Weeks) = Total Calorie Deficit Needed (kcal) / Weekly Calorie Deficit (kcal)
Example Calculation:
Let's say:
Current Weight: 80 kg
Target Weight: 70 kg
Weekly Calorie Deficit: 1000 kcal
1. Total Weight Loss: 80 kg – 70 kg = 10 kg
2. Total Calorie Deficit Needed: 10 kg * 7700 kcal/kg = 77,000 kcal
3. Estimated Time: 77,000 kcal / 1000 kcal/week = 77 weeks
In this example, it would take approximately 77 weeks (about 1 year and 5 months) to reach the target weight if a consistent 1000 kcal deficit is maintained weekly.
Important Considerations:
This calculator provides an estimate. Individual results can vary significantly due to metabolism, exercise intensity, muscle mass, hormonal factors, and adherence to the deficit.
A safe and sustainable weekly weight loss rate is typically between 0.5 kg to 1 kg (approximately 1-2 lbs). Larger deficits can lead to muscle loss, nutrient deficiencies, and are harder to maintain long-term.
Consulting a healthcare professional or a registered dietitian is highly recommended before starting any significant weight loss program.
This calculator is for informational purposes only and does not constitute medical advice. Always consult with a qualified healthcare provider for any health concerns or before making any decisions related to your health or treatment.
function calculateWeightLossDuration() {
var currentWeight = parseFloat(document.getElementById("currentWeight").value);
var targetWeight = parseFloat(document.getElementById("targetWeight").value);
var weeklyDeficit = parseFloat(document.getElementById("weeklyDeficit").value);
var resultValueElement = document.getElementById("result-value");
var resultUnitElement = document.getElementById("result-unit");
// Clear previous results
resultValueElement.innerHTML = "–";
resultUnitElement.innerHTML = "–";
// Validate inputs
if (isNaN(currentWeight) || currentWeight <= 0) {
alert("Please enter a valid current weight.");
return;
}
if (isNaN(targetWeight) || targetWeight <= 0) {
alert("Please enter a valid target weight.");
return;
}
if (isNaN(weeklyDeficit) || weeklyDeficit = currentWeight) {
alert("Your target weight must be less than your current weight.");
return;
}
var weightToLose = currentWeight – targetWeight;
var totalCalorieDeficitNeeded = weightToLose * 7700; // 7700 kcal per kg of fat
var estimatedWeeks = totalCalorieDeficitNeeded / weeklyDeficit;
resultValueElement.innerHTML = estimatedWeeks.toFixed(1);
resultUnitElement.innerHTML = "Weeks";
}