Calculate exactly how many calories you need to eat to reach your weight loss goals safely.
Sedentary (Little to no exercise)
Lightly Active (1-3 days/week)
Moderately Active (3-5 days/week)
Very Active (6-7 days/week)
Extra Active (Physical job or training)
Achieving weight loss comes down to a fundamental scientific principle: thermodynamics. To lose fat, you must consume fewer calories than your body burns on a daily basis. This calculator uses your personal data to determine your Basal Metabolic Rate (BMR) and Total Daily Energy Expenditure (TDEE) to provide a precise calorie target.
What is TDEE and why does it matter?
Your TDEE (Total Daily Energy Expenditure) is the total number of calories you burn in a day, including:
Basal Metabolic Rate (BMR): Calories burned just to keep your organs functioning while at rest.
Physical Activity: Calories burned during exercise and movement.
Thermic Effect of Food: Calories burned digesting what you eat.
To maintain your current weight, you would eat at your TDEE level. To lose weight, you must eat below this number.
How to Interpret Your Calorie Target
The "Daily Calorie Target" displayed above represents your "sweet spot." It subtracts enough calories to stimulate fat loss (the deficit) but keeps enough to fuel your body and preserve muscle mass.
For example, a deficit of 500 calories per day typically results in 1 pound of weight loss per week (since 1 pound of fat roughly equals 3,500 calories). While it might be tempting to select the "Extreme" setting, research shows that a moderate deficit (0.5 to 1 lb per week) is more sustainable long-term and reduces the risk of metabolic adaptation.
Tips for Success
Track Accurately: Use a food scale and a tracking app to ensure you are actually hitting your daily target.
Prioritize Protein: Eating high protein helps preserve muscle mass while in a calorie deficit.
Re-calculate Often: As you lose weight, your TDEE will decrease. Re-visit this calculator every 5-10 lbs lost to adjust your numbers.
Don't Eat Back Exercise Calories: Activity trackers often overestimate burns. Stick to the activity level you selected in the calculator rather than adding extra calories for every workout.
Is a Calorie Deficit Safe?
Yes, a controlled calorie deficit is the standard, safe method for weight loss recommended by health organizations. However, it is generally advised not to drop below 1,200 calories (for women) or 1,500 calories (for men) per day without medical supervision, as it becomes difficult to get essential micronutrients below these intakes.
function calculateCalories() {
// 1. Get input values
var age = parseFloat(document.getElementById("age").value);
var heightFeet = parseFloat(document.getElementById("heightFeet").value);
var heightInches = parseFloat(document.getElementById("heightInches").value);
var weightLbs = parseFloat(document.getElementById("weight").value);
var activityMultiplier = parseFloat(document.getElementById("activity").value);
var deficitGoal = parseFloat(document.getElementById("goal").value);
// Handle gender radio button
var gender = "male";
if (document.getElementById("genderFemale").checked) {
gender = "female";
}
// 2. Validate inputs
if (isNaN(age) || isNaN(heightFeet) || isNaN(heightInches) || isNaN(weightLbs)) {
alert("Please enter valid numbers for Age, Height, and Weight.");
return;
}
// 3. Conversions
// Weight: Lbs to Kg (1 lb = 0.453592 kg)
var weightKg = weightLbs * 0.453592;
// Height: Feet/Inches to cm (1 inch = 2.54 cm)
var totalInches = (heightFeet * 12) + heightInches;
var heightCm = totalInches * 2.54;
// 4. Calculate BMR (Mifflin-St Jeor Equation)
var bmr = 0;
if (gender === "male") {
// Men: (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) + 5
bmr = (10 * weightKg) + (6.25 * heightCm) – (5 * age) + 5;
} else {
// Women: (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) – 161
bmr = (10 * weightKg) + (6.25 * heightCm) – (5 * age) – 161;
}
// 5. Calculate TDEE
var tdee = bmr * activityMultiplier;
// 6. Calculate Target Calories
var targetCalories = tdee – deficitGoal;
// Safety floor check (optional but recommended for UX)
var safetyWarning = "";
var minimum = (gender === "male") ? 1500 : 1200;
if (targetCalories < minimum) {
// Don't error out, but maybe adjust logic or just var user see low number?
// For a simple calculator, we just show the number but ensure it's not negative.
if (targetCalories < 0) targetCalories = 0;
}
// 7. Update DOM
document.getElementById("tdeeResult").innerText = Math.round(tdee) + " kcal";
document.getElementById("deficitResult").innerText = "-" + deficitGoal + " kcal";
document.getElementById("targetResult").innerText = Math.round(targetCalories) + " kcal";
// Show result section
document.getElementById("result-section").style.display = "block";
}