0.25 kg per week (Slow & Sustainable)
0.5 kg per week (Moderate)
0.75 kg per week (Faster)
1 kg per week (Aggressive – Consult Doctor)
You can estimate your BMR using online calculators or formulas like Harris-Benedict.
Sedentary (little to no exercise)
Lightly Active (light exercise/sports 1-3 days/week)
Moderately Active (moderate exercise/sports 3-5 days/week)
Very Active (hard exercise/sports 6-7 days/week)
Extra Active (very hard exercise/sports & physical job)
Your target daily calorie intake will be displayed here.
Understanding Your Weight Loss Calorie Needs
Losing weight effectively and sustainably requires understanding the fundamental principle of energy balance: consuming fewer calories than your body expends. This calculator helps you determine a personalized daily calorie target to achieve your desired weight loss.
The Science Behind the Calculation
Weight loss is primarily driven by creating a calorie deficit. A deficit of approximately 3,500 calories is generally needed to lose one pound (about 0.45 kg) of fat. Our calculator uses this principle, along with your BMR and activity level, to estimate your daily needs.
1. Basal Metabolic Rate (BMR):
Your BMR is the number of calories your body burns at rest to maintain basic life-sustaining functions like breathing, circulation, and cell production. It's the foundation of your daily energy expenditure. You can estimate BMR using formulas like the Harris-Benedict or Mifflin-St Jeor equations, or use an online BMR calculator.
2. Total Daily Energy Expenditure (TDEE):
TDEE is your BMR plus the calories you burn through physical activity and the thermic effect of food. We estimate TDEE by multiplying your BMR by an activity factor based on your lifestyle:
Sedentary: 1.2
Lightly Active: 1.375
Moderately Active: 1.55
Very Active: 1.725
Extra Active: 1.9
Formula: TDEE = BMR × Activity Factor
3. Creating a Calorie Deficit:
To lose weight, you need to consume fewer calories than your TDEE. The calculator determines the daily deficit required to meet your desired weekly weight loss rate:
A weekly loss of 0.25 kg requires a deficit of approximately 1750 calories per week (0.25 kg * 3500 kcal/kg / 7 days).
A weekly loss of 0.5 kg requires a deficit of approximately 3500 calories per week (0.5 kg * 3500 kcal/kg / 7 days).
A weekly loss of 0.75 kg requires a deficit of approximately 5250 calories per week (0.75 kg * 3500 kcal/kg / 7 days).
A weekly loss of 1 kg requires a deficit of approximately 7000 calories per week (1 kg * 3500 kcal/kg / 7 days).
Current Weight & Target Weight: Enter your current weight and the weight you aim to achieve in kilograms.
Desired Weekly Weight Loss: Select a realistic rate of weight loss. Losing 0.5 kg to 1 kg per week is generally considered safe and sustainable. Faster rates may be difficult to maintain and could be unhealthy without medical supervision.
Basal Metabolic Rate (BMR): Input your estimated BMR. If you don't know it, you can use an online calculator or a standard formula.
Activity Level: Choose the option that best reflects your typical daily physical activity.
Important Considerations:
This calculator provides an estimation. Individual metabolisms can vary.
A minimum calorie intake of 1200 kcal/day for women and 1500 kcal/day for men is generally recommended to ensure adequate nutrient intake. Consult a healthcare professional if your calculated target falls below these levels.
Sustainable weight loss involves a balanced diet and regular exercise.
Always consult with a doctor or registered dietitian before making significant changes to your diet or exercise routine, especially if you have underlying health conditions.
function calculateCalories() {
var currentWeight = parseFloat(document.getElementById("currentWeight").value);
var targetWeight = parseFloat(document.getElementById("targetWeight").value);
var weightLossRate = parseFloat(document.getElementById("weightLossRate").value);
var bmr = parseFloat(document.getElementById("bmr").value);
var activityLevel = parseFloat(document.getElementById("activityLevel").value);
var resultDiv = document.getElementById("result");
// Input validation
if (isNaN(currentWeight) || isNaN(targetWeight) || isNaN(weightLossRate) || isNaN(bmr) || isNaN(activityLevel)) {
resultDiv.innerHTML = "Please enter valid numbers for all fields.";
resultDiv.style.color = "#dc3545"; // Red for error
resultDiv.style.borderColor = "#dc3545";
return;
}
if (currentWeight <= 0 || targetWeight <= 0 || bmr <= 0) {
resultDiv.innerHTML = "Weight and BMR must be positive values.";
resultDiv.style.color = "#dc3545"; // Red for error
resultDiv.style.borderColor = "#dc3545";
return;
}
if (weightLossRate <= 0) {
resultDiv.innerHTML = "Desired weekly weight loss must be a positive value.";
resultDiv.style.color = "#dc3545"; // Red for error
resultDiv.style.borderColor = "#dc3545";
return;
}
if (currentWeight <= targetWeight) {
resultDiv.innerHTML = "Your target weight should be less than your current weight for weight loss.";
resultDiv.style.color = "#dc3545"; // Red for error
resultDiv.style.borderColor = "#dc3545";
return;
}
// Calculate TDEE (Total Daily Energy Expenditure)
var tdee = bmr * activityLevel;
// Calculate daily calorie deficit needed for desired weekly loss
// 1 kg of fat is approximately 7700 calories (use 3500 per pound for approx kg calculation)
var caloriesPerKgFat = 7700;
var dailyDeficit = (weightLossRate * caloriesPerKgFat) / 7;
// Calculate target daily calorie intake
var targetDailyCalories = tdee – dailyDeficit;
// Ensure minimum recommended calorie intake is considered
var minCaloriesWomen = 1200;
var minCaloriesMen = 1500; // Defaulting to men's minimum for general recommendation
var finalTargetCalories = targetDailyCalories;
if (targetDailyCalories < minCaloriesWomen) {
finalTargetCalories = minCaloriesWomen;
resultDiv.innerHTML = "Your calculated target daily calories (" + targetDailyCalories.toFixed(0) + " kcal) is below the recommended minimum. Aim for at least " + minCaloriesWomen + " kcal. Consider adjusting your weight loss rate or activity level.";
resultDiv.style.color = "#ffc107"; // Yellow for warning
resultDiv.style.borderColor = "#ffc107";
} else {
resultDiv.innerHTML = "Your estimated target daily calorie intake is: " + finalTargetCalories.toFixed(0) + " kcal per day.";
resultDiv.style.color = "#28a745"; // Green for success
resultDiv.style.borderColor = "#28a745";
}
}