Sedentary (Office job, little exercise)
Light Activity (Exercise 1-3 days/week)
Moderate Activity (Exercise 3-5 days/week)
Very Active (Exercise 6-7 days/week)
Extra Active (Physical job or training 2x/day)
Mild Weight Loss (0.5 lbs/week)
Standard Weight Loss (1 lb/week)
Extreme Weight Loss (2 lbs/week)
Your Daily Calorie Targets
Maintenance Calories (TDEE):2,000 kcal
Daily Deficit:-500 kcal
Target Daily Intake:1,500 kcal
*This target includes your Base Metabolic Rate and Activity Level adjustments.
Understanding the Science of a Calorie Deficit
Achieving weight loss is fundamentally a matter of energy balance. A calorie deficit occurs when you consume fewer calories than your body expends for energy. This forces your body to tap into stored energy reserves, primarily adipose tissue (fat), to function.
How This Calculator Works
This tool uses the Mifflin-St Jeor Equation, widely considered by clinical nutritionists to be the most accurate formula for estimating Basal Metabolic Rate (BMR). Your BMR represents the energy your body needs just to keep your organs functioning at rest.
However, you don't stay in bed all day. We multiply your BMR by an Activity Factor to determine your Total Daily Energy Expenditure (TDEE). This is your "maintenance" number—the amount you would need to eat to stay the exact same weight.
Setting Safe Goals
To lose weight, you subtract calories from your TDEE. Health experts generally recommend the following guidelines:
0.5 lbs per week: Requires a ~250 daily calorie deficit. Sustainable and minimizes muscle loss.
1 lb per week: Requires a ~500 daily calorie deficit. The "Gold Standard" for steady progress.
2 lbs per week: Requires a ~1,000 daily calorie deficit. Aggressive; usually only recommended for individuals with higher starting body fat percentages.
The Importance of Protein
When in a calorie deficit, your body may try to break down muscle tissue for energy. To prevent this, ensure you maintain a high protein intake (roughly 0.8g to 1g per pound of body weight) and engage in resistance training. This signals your body to burn fat while preserving lean muscle mass.
function calculateDeficit() {
// 1. Get Input Values
var gender = document.getElementById('cd_gender').value;
var age = parseFloat(document.getElementById('cd_age').value);
var weightLbs = parseFloat(document.getElementById('cd_weight').value);
var heightFt = parseFloat(document.getElementById('cd_height_ft').value);
var heightIn = parseFloat(document.getElementById('cd_height_in').value);
var activityLevel = parseFloat(document.getElementById('cd_activity').value);
var deficitGoal = parseFloat(document.getElementById('cd_goal').value);
// 2. Validation
if (isNaN(age) || isNaN(weightLbs) || isNaN(heightFt) || isNaN(heightIn)) {
alert("Please enter valid numbers for Age, Weight, and Height.");
return;
}
if (age 100) {
alert("Please enter a valid age between 10 and 100.");
return;
}
// 3. Conversions (Imperial to Metric)
// 1 lb = 0.453592 kg
// 1 inch = 2.54 cm
var weightKg = weightLbs * 0.453592;
var totalInches = (heightFt * 12) + heightIn;
var heightCm = totalInches * 2.54;
// 4. Calculate BMR (Mifflin-St Jeor Equation)
// Men: (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) + 5
// Women: (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) – 161
var bmr = 0;
if (gender === 'male') {
bmr = (10 * weightKg) + (6.25 * heightCm) – (5 * age) + 5;
} else {
bmr = (10 * weightKg) + (6.25 * heightCm) – (5 * age) – 161;
}
// 5. Calculate TDEE and Target
var tdee = bmr * activityLevel;
var targetCalories = tdee – deficitGoal;
// Safety check: Don't recommend dangerously low calories
var minCalories = (gender === 'male') ? 1500 : 1200;
var warningMsg = "";
if (targetCalories < minCalories) {
targetCalories = minCalories;
warningMsg = " (Adjusted to minimum safe limit)";
}
// 6. Display Results
document.getElementById('cd-result-display').style.display = "block";
// Format numbers with commas
document.getElementById('cd_tdee_result').innerHTML = Math.round(tdee).toLocaleString() + " kcal";
document.getElementById('cd_deficit_val').innerHTML = "-" + deficitGoal + " kcal";
document.getElementById('cd_final_target').innerHTML = Math.round(targetCalories).toLocaleString() + " kcal" + warningMsg;
// Smooth scroll to result
document.getElementById('cd-result-display').scrollIntoView({ behavior: 'smooth' });
}