Sedentary (Little to no exercise)
Lightly Active (Exercise 1-3 days/week)
Moderately Active (Exercise 3-5 days/week)
Very Active (Exercise 6-7 days/week)
Extra Active (Very hard exercise/physical job)
Your Results
Basal Metabolic Rate (BMR):0 kcal
Maintenance Calories (TDEE):0 kcal
Recommended Intake for Weight Loss:
Mild Weight Loss (-0.25 kg/week):0 kcal
Moderate Weight Loss (-0.5 kg/week):0 kcal
Extreme Weight Loss (-1 kg/week):0 kcal
*Never consume fewer than 1200 calories (women) or 1500 calories (men) without medical supervision.
function calculateDeficit() {
// 1. Get Inputs
var gender = document.getElementById('cdc-gender').value;
var age = parseFloat(document.getElementById('cdc-age').value);
var weight = parseFloat(document.getElementById('cdc-weight').value);
var height = parseFloat(document.getElementById('cdc-height').value);
var activityMultiplier = parseFloat(document.getElementById('cdc-activity').value);
// 2. Validation
if (isNaN(age) || isNaN(weight) || isNaN(height)) {
alert("Please enter valid numbers for Age, Weight, and Height.");
return;
}
// 3. Logic: Mifflin-St Jeor Equation
var bmr;
if (gender === 'male') {
// (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) + 5
bmr = (10 * weight) + (6.25 * height) – (5 * age) + 5;
} else {
// (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) – 161
bmr = (10 * weight) + (6.25 * height) – (5 * age) – 161;
}
// Calculate Total Daily Energy Expenditure (TDEE)
var tdee = bmr * activityMultiplier;
// Calculate Deficits (1kg of fat ≈ 7700 calories)
// 0.25kg/week = ~275 kcal/day deficit
// 0.5kg/week = ~550 kcal/day deficit
// 1kg/week = ~1100 kcal/day deficit
var mildLoss = tdee – 250;
var moderateLoss = tdee – 500;
var extremeLoss = tdee – 1000;
// Safety floors
var minCalories = (gender === 'male') ? 1500 : 1200;
// 4. Update UI
document.getElementById('res-bmr').innerHTML = Math.round(bmr) + " kcal";
document.getElementById('res-tdee').innerHTML = Math.round(tdee) + " kcal";
document.getElementById('res-mild').innerHTML = Math.round(mildLoss) + " kcal";
document.getElementById('res-mod').innerHTML = Math.round(moderateLoss) + " kcal";
// Handle unsafe extreme deficits
var extElement = document.getElementById('res-ext');
if (extremeLoss < minCalories) {
extElement.innerHTML = "Not Recommended (< " + minCalories + ")";
extElement.style.color = "#dc3545";
} else {
extElement.innerHTML = Math.round(extremeLoss) + " kcal";
extElement.style.color = "#212529";
}
document.getElementById('cdc-result').style.display = 'block';
}
Understanding Calorie Deficit for Weight Loss
Achieving a sustainable weight loss journey begins with the fundamental principle of energy balance: Calories In vs. Calories Out. To lose weight, you must consume fewer calories than your body burns, creating what is known as a calorie deficit. This calculator helps you estimate the precise number of calories you need to eat daily to reach your goals safely.
What is BMR and TDEE?
Before calculating your deficit, it is crucial to understand two key metrics used in our calculator:
BMR (Basal Metabolic Rate): This is the number of calories your body needs to perform basic life-sustaining functions like breathing, circulation, and cell production while at complete rest.
TDEE (Total Daily Energy Expenditure): This is your BMR multiplied by an activity factor. It represents the total calories you burn in a day, including exercise and daily movements. Eating at your TDEE will maintain your current weight.
How to Calculate Your Calorie Deficit
The standard scientific approach to weight loss suggests that a deficit of approximately 3,500 to 7,700 calories is required to lose 1 kilogram of body fat. Breaking this down into daily goals:
A daily deficit of 500 calories results in approximately 0.5 kg (1.1 lbs) of weight loss per week.
A daily deficit of 1,000 calories results in approximately 1 kg (2.2 lbs) of weight loss per week.
However, aggressive deficits can be counterproductive, leading to muscle loss and metabolic adaptation. Most nutritionists recommend a moderate deficit of 300-500 calories below your TDEE.
Safety Guidelines
While cutting calories is necessary for fat loss, eating too little can be dangerous. As a general rule of thumb, women should not consume fewer than 1,200 calories per day, and men should not consume fewer than 1,500 calories per day unless under direct medical supervision. Extremely low-calorie intakes can lead to nutrient deficiencies, fatigue, and a "rebound" effect where weight is regained quickly.
Tips for Maintaining a Deficit
Sticking to a calorie deficit can be challenging. Here are strategies to make it easier:
Prioritize Protein: Protein has a high thermic effect and keeps you feeling full longer than carbohydrates or fats.
Volume Eating: Fill up on low-calorie, high-volume foods like leafy greens and vegetables.
Track Accurately: Use a food scale and tracking app to ensure you aren't underestimating your intake.
Strength Training: Lifting weights helps preserve muscle mass while in a deficit, ensuring the weight you lose is primarily fat.