Calorie Calculator for Weight Loss
Use this calculator to estimate your Basal Metabolic Rate (BMR), Total Daily Energy Expenditure (TDEE), and the recommended daily calorie intake to achieve your weight loss goals. This tool uses the Mifflin-St Jeor equation for BMR, which is considered one of the most accurate.
function calculateCalories() {
var gender = document.getElementById('gender').value;
var age = parseFloat(document.getElementById('age').value);
var weightLbs = parseFloat(document.getElementById('weightLbs').value);
var heightInches = parseFloat(document.getElementById('heightInches').value);
var activityLevel = document.getElementById('activityLevel').value;
var weightLossGoal = parseFloat(document.getElementById('weightLossGoal').value);
var resultContainer = document.getElementById('resultContainer');
var resultBMR = document.getElementById('resultBMR');
var resultTDEE = document.getElementById('resultTDEE');
var resultTargetCalories = document.getElementById('resultTargetCalories');
var warningMessage = document.getElementById('warningMessage');
warningMessage.innerHTML = "; // Clear previous warnings
if (!gender || isNaN(age) || age <= 0 || isNaN(weightLbs) || weightLbs <= 0 || isNaN(heightInches) || heightInches <= 0 || !activityLevel || isNaN(weightLossGoal) || weightLossGoal <= 0) {
alert('Please fill in all fields with valid positive numbers.');
resultContainer.style.display = 'none';
return;
}
// Convert lbs to kg and inches to cm
var weightKg = weightLbs * 0.453592;
var heightCm = heightInches * 2.54;
var bmr;
// Mifflin-St Jeor Equation
if (gender === 'male') {
bmr = (10 * weightKg) + (6.25 * heightCm) – (5 * age) + 5;
} else if (gender === 'female') {
bmr = (10 * weightKg) + (6.25 * heightCm) – (5 * age) – 161;
} else {
alert('Please select a valid gender.');
resultContainer.style.display = 'none';
return;
}
var activityFactor;
switch (activityLevel) {
case 'sedentary':
activityFactor = 1.2;
break;
case 'lightlyActive':
activityFactor = 1.375;
break;
case 'moderatelyActive':
activityFactor = 1.55;
break;
case 'veryActive':
activityFactor = 1.725;
break;
case 'extraActive':
activityFactor = 1.9;
break;
default:
alert('Please select a valid activity level.');
resultContainer.style.display = 'none';
return;
}
var tdee = bmr * activityFactor;
// 1 lb of fat is approximately 3500 calories
// Daily deficit for weight loss goal
var dailyCalorieDeficit = (weightLossGoal * 3500) / 7;
var targetCalories = tdee – dailyCalorieDeficit;
// Minimum calorie intake recommendations
var minCalories = (gender === 'female') ? 1200 : 1500;
if (targetCalories < minCalories) {
warningMessage.innerHTML = 'Warning: The calculated calorie intake (' + Math.round(targetCalories) + ' calories) is below the generally recommended minimum of ' + minCalories + ' calories per day for your gender. Consuming too few calories can be detrimental to your health. Consider a slower weight loss goal or consult a healthcare professional.';
targetCalories = minCalories; // Adjust to minimum for display, but warn user
}
resultBMR.textContent = Math.round(bmr);
resultTDEE.textContent = Math.round(tdee);
resultTargetCalories.textContent = Math.round(targetCalories);
resultContainer.style.display = 'block';
}
.calorie-calculator-container {
font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
max-width: 600px;
margin: 20px auto;
padding: 25px;
border: 1px solid #e0e0e0;
border-radius: 8px;
background-color: #ffffff;
box-shadow: 0 4px 12px rgba(0, 0, 0, 0.05);
}
.calorie-calculator-container h2 {
text-align: center;
color: #333;
margin-bottom: 20px;
font-size: 26px;
}
.calorie-calculator-container p {
font-size: 15px;
line-height: 1.6;
color: #555;
margin-bottom: 15px;
}
.calculator-form .form-group {
margin-bottom: 18px;
}
.calculator-form label {
display: block;
margin-bottom: 8px;
font-weight: bold;
color: #444;
font-size: 15px;
}
.calculator-form input[type="number"],
.calculator-form select {
width: calc(100% – 22px);
padding: 12px 10px;
border: 1px solid #ccc;
border-radius: 5px;
font-size: 16px;
color: #333;
box-sizing: border-box;
transition: border-color 0.3s ease;
}
.calculator-form input[type="number"]:focus,
.calculator-form select:focus {
border-color: #007bff;
outline: none;
box-shadow: 0 0 0 2px rgba(0, 123, 255, 0.25);
}
.calculator-form button {
display: block;
width: 100%;
padding: 14px 20px;
background-color: #007bff;
color: white;
border: none;
border-radius: 5px;
font-size: 18px;
font-weight: bold;
cursor: pointer;
transition: background-color 0.3s ease, transform 0.2s ease;
margin-top: 25px;
}
.calculator-form button:hover {
background-color: #0056b3;
transform: translateY(-2px);
}
#resultContainer h3 {
color: #333;
margin-top: 0;
margin-bottom: 15px;
font-size: 22px;
border-bottom: 1px solid #eee;
padding-bottom: 10px;
}
#resultContainer p {
font-size: 16px;
color: #333;
margin-bottom: 10px;
}
#resultContainer p strong {
color: #007bff;
}
Understanding Your Calorie Needs for Weight Loss
Losing weight effectively often comes down to creating a consistent calorie deficit – consuming fewer calories than your body burns. This calculator helps you estimate the key numbers needed to achieve this, but it's important to understand what they mean.
Basal Metabolic Rate (BMR)
Your Basal Metabolic Rate (BMR) is the number of calories your body needs to perform basic, life-sustaining functions while at rest. This includes breathing, circulation, cell production, nutrient processing, and maintaining body temperature. It's the minimum energy required to keep you alive, even if you were to do nothing but sleep all day. Factors like age, gender, weight, and height significantly influence your BMR.
Total Daily Energy Expenditure (TDEE)
While BMR accounts for your resting energy needs, your Total Daily Energy Expenditure (TDEE) is the total number of calories your body burns in a 24-hour period, taking into account your BMR and your physical activity level. This includes calories burned during exercise, daily movements (like walking, standing), and even the energy used to digest food (thermic effect of food). Your activity level plays a crucial role in determining your TDEE:
- Sedentary: Little or no exercise.
- Lightly Active: Light exercise or sports 1-3 days per week.
- Moderately Active: Moderate exercise or sports 3-5 days per week.
- Very Active: Hard exercise or sports 6-7 days a week.
- Extra Active: Very hard exercise, a physical job, or training twice a day.
Creating a Calorie Deficit for Weight Loss
To lose weight, you need to consume fewer calories than your TDEE. This difference is called a calorie deficit. A common guideline is that a deficit of 3,500 calories equates to approximately one pound of fat loss. Therefore, to lose one pound per week, you would aim for a daily deficit of 500 calories (3,500 calories / 7 days).
This calculator provides a recommended daily calorie intake by subtracting your chosen weekly weight loss goal (converted to a daily calorie deficit) from your estimated TDEE. It's generally recommended not to create an excessively large deficit, as this can lead to nutrient deficiencies, muscle loss, and make the diet unsustainable. For most individuals, a deficit leading to 1-2 pounds of weight loss per week is considered healthy and sustainable.
Important Considerations
- These are Estimates: All calorie calculators provide estimates. Individual metabolism can vary, and factors like genetics, hormones, and body composition can influence your actual calorie needs.
- Minimum Calorie Intake: It's generally not recommended for women to consume fewer than 1200 calories per day and men fewer than 1500 calories per day without medical supervision, as this can lead to nutritional deficiencies and health problems.
- Consult a Professional: For personalized advice, especially if you have underlying health conditions or significant weight loss goals, always consult with a doctor or a registered dietitian.
- Beyond Calories: While calories are key, the quality of your diet matters. Focus on nutrient-dense foods, adequate protein, healthy fats, and plenty of fruits and vegetables for overall health and sustainable weight loss.