Use this calculator to estimate your potential weight loss over a specified period by adjusting your daily calorie intake and exercise.
Sedentary (little or 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 a week)
Extra active (very hard exercise/physical job)
Understanding Your Projected Weight Loss
Achieving sustainable weight loss is primarily about creating a consistent calorie deficit – consuming fewer calories than your body burns. This calculator helps you estimate your potential weight loss over a specific period by taking into account your current body metrics, activity level, and your planned dietary and exercise changes.
How the Calculator Works
The calculator uses established formulas to provide an estimate:
Basal Metabolic Rate (BMR): This is the number of calories your body burns at rest to maintain basic bodily functions (breathing, circulation, cell production, etc.). The Mifflin-St Jeor equation is used, which is considered one of the most accurate for estimating BMR.
Total Daily Energy Expenditure (TDEE): Your TDEE is your BMR multiplied by an activity factor. This accounts for the calories you burn through daily activities, work, and exercise.
Calorie Deficit: This is the difference between your TDEE (calories burned) and your target daily calorie intake, plus any additional calories burned through dedicated exercise. A deficit of approximately 3500 calories typically results in a loss of one pound of body fat.
Projected Weight Loss: By multiplying your daily calorie deficit by the number of days in your calculation period and dividing by 3500, the calculator estimates your total weight loss in pounds.
Key Inputs Explained:
Current Weight, Height, Age, Gender: These are crucial for accurately calculating your BMR.
Activity Level: This factor adjusts your BMR to estimate your TDEE, reflecting how much energy you expend through daily movement and exercise.
Target Daily Calorie Intake: This is the number of calories you plan to consume each day. Be realistic and aim for a deficit that is sustainable and healthy (typically 500-1000 calories below your TDEE for 1-2 lbs/week loss).
Daily Exercise Calories Burned: This accounts for additional calories burned through structured exercise sessions, further contributing to your daily deficit.
Calculation Period (weeks): The duration over which you want to project your weight loss.
Example Calculation:
Let's consider a 35-year-old female, 5'6″ (66 inches), weighing 180 lbs, who is moderately active. She plans to reduce her daily calorie intake to 1600 calories and burn an additional 200 calories through exercise daily. She wants to know her projected weight loss over 8 weeks.
This calculator provides an estimate. Actual weight loss can vary due to individual metabolism, body composition, hormonal factors, and adherence to the plan. It's crucial to:
Consult a Healthcare Professional: Before starting any new diet or exercise program, especially if you have underlying health conditions.
Focus on Sustainable Habits: Rapid weight loss is often unsustainable. Aim for a healthy and gradual loss of 1-2 pounds per week.
Nutrient Density: Ensure your target calorie intake still provides adequate nutrition.
Listen to Your Body: Adjust your plan if you feel unwell or overly fatigued.
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function calculateWeightLoss() {
// Get input values
var currentWeightLbs = parseFloat(document.getElementById("currentWeight").value);
var heightFeet = parseFloat(document.getElementById("heightFeet").value);
var heightInches = parseFloat(document.getElementById("heightInches").value);
var age = parseFloat(document.getElementById("age").value);
var genderMale = document.getElementById("genderMale").checked;
var activityLevelFactor = parseFloat(document.getElementById("activityLevel").value);
var targetCalorieIntake = parseFloat(document.getElementById("targetCalorieIntake").value);
var dailyExerciseCalories = parseFloat(document.getElementById("dailyExerciseCalories").value);
var calculationPeriodWeeks = parseFloat(document.getElementById("calculationPeriod").value);
// Validate inputs
if (isNaN(currentWeightLbs) || currentWeightLbs <= 0 ||
isNaN(heightFeet) || heightFeet < 0 ||
isNaN(heightInches) || heightInches = 12 ||
isNaN(age) || age <= 0 ||
isNaN(targetCalorieIntake) || targetCalorieIntake <= 0 ||
isNaN(dailyExerciseCalories) || dailyExerciseCalories < 0 ||
isNaN(calculationPeriodWeeks) || calculationPeriodWeeks <= 0) {
document.getElementById("result").innerHTML = "Please enter valid positive numbers for all fields.";
return;
}
// Conversions
var totalHeightInches = (heightFeet * 12) + heightInches;
var currentWeightKg = currentWeightLbs / 2.20462;
var heightCm = totalHeightInches * 2.54;
// Calculate BMR (Mifflin-St Jeor Equation)
var bmr;
if (genderMale) {
bmr = (10 * currentWeightKg) + (6.25 * heightCm) – (5 * age) + 5;
} else { // Female
bmr = (10 * currentWeightKg) + (6.25 * heightCm) – (5 * age) – 161;
}
// Calculate TDEE
var tdee = bmr * activityLevelFactor;
// Calculate Net Daily Calorie Deficit
var dailyCalorieDeficit = tdee – targetCalorieIntake + dailyExerciseCalories;
// Check for calorie surplus
if (dailyCalorieDeficit <= 0) {
document.getElementById("result").innerHTML = "Your current plan results in a calorie surplus or no deficit. You need to create a calorie deficit to lose weight." +
"Estimated TDEE: " + tdee.toFixed(0) + " calories/day" +
"To lose weight, your Target Daily Calorie Intake + Daily Exercise Calories Burned should be less than your TDEE.";
return;
}
// Calculate Projected Weight Loss
var totalDays = calculationPeriodWeeks * 7;
var totalCalorieDeficit = dailyCalorieDeficit * totalDays;
var projectedWeightLossLbs = totalCalorieDeficit / 3500; // 3500 calories per pound of fat
// Calculate Projected New Weight
var projectedNewWeightLbs = currentWeightLbs – projectedWeightLossLbs;
// Display results
var resultHtml = "
Your Projected Weight Loss:
";
resultHtml += "Estimated BMR: " + bmr.toFixed(0) + " calories/day";
resultHtml += "Estimated TDEE (Total Daily Energy Expenditure): " + tdee.toFixed(0) + " calories/day";
resultHtml += "Your Net Daily Calorie Deficit: " + dailyCalorieDeficit.toFixed(0) + " calories/day";
resultHtml += "Projected Weight Loss over " + calculationPeriodWeeks + " weeks: " + projectedWeightLossLbs.toFixed(1) + " lbs";
resultHtml += "Projected New Weight: " + projectedNewWeightLbs.toFixed(1) + " lbs";
resultHtml += "(Based on a 3500 calorie deficit per pound of fat)";
document.getElementById("result").innerHTML = resultHtml;
}