Counting Calories to Lose Weight Calculator

Calorie Deficit & Weight Loss Calculator

Calculate your daily calories to reach your goal weight

Male Female
Sedentary (Office job, little to no exercise) Lightly Active (Light exercise 1-3 days/week) Moderately Active (Moderate exercise 3-5 days/week) Very Active (Hard exercise 6-7 days/week) Extra Active (Physical job + hard training)

Your Daily Results

Maintain Weight 0 kcal
Weight Loss (0.5kg/week) 0 kcal
Extreme Loss (1kg/week) 0 kcal

*Warning: It is generally not recommended to consume fewer than 1,200 (women) or 1,500 (men) calories per day without medical supervision.


How to Use Counting Calories to Lose Weight

Weight loss is fundamentally driven by the law of thermodynamics: energy in versus energy out. To lose weight, you must create a caloric deficit, meaning you consume fewer calories than your body burns to maintain its current mass.

Understanding the Calculation

Our calculator uses the Mifflin-St Jeor Equation, which is widely considered the most accurate standard for estimating Basal Metabolic Rate (BMR). Your BMR is the number of calories your body needs to function (breathe, pump blood, regulate temperature) while at complete rest.

  • Maintenance: This is your TDEE (Total Daily Energy Expenditure). If you eat this amount, your weight stays the same.
  • Weight Loss: Calculated by subtracting 500 calories from your TDEE. This creates a deficit of 3,500 calories per week, which roughly equates to 0.5kg (1lb) of fat loss.
  • Extreme Loss: A 1,000-calorie daily deficit. This should be approached with caution and usually incorporates both diet and increased exercise.

Real-World Example

Consider Sarah, a 35-year-old female who weighs 85kg and is 165cm tall. She works a desk job (Sedentary).

  1. BMR Calculation: (10 × 85) + (6.25 × 165) – (5 × 35) – 161 = 1,545 calories.
  2. TDEE Calculation: 1,545 × 1.2 (Sedentary) = 1,854 calories per day to maintain weight.
  3. Weight Loss Goal: To lose 0.5kg a week, Sarah targets 1,354 calories daily.

Tips for Successful Calorie Counting

1. Invest in a food scale: Volume measurements (cups, spoons) are often inaccurate. Weighing food in grams provides the most precise data.

2. Don't forget the liquids: Oils, sauces, and sugary drinks are calorie-dense and often overlooked. Even a tablespoon of olive oil adds 120 calories.

3. Prioritize Protein: Eating enough protein helps preserve muscle mass during a caloric deficit and keeps you feeling full longer.

function calculateCalorieNeeds() { var gender = document.getElementById('calGender').value; var age = parseFloat(document.getElementById('calAge').value); var weight = parseFloat(document.getElementById('calWeight').value); var height = parseFloat(document.getElementById('calHeight').value); var activity = parseFloat(document.getElementById('calActivity').value); if (isNaN(age) || isNaN(weight) || isNaN(height) || age <= 0 || weight <= 0 || height <= 0) { alert("Please enter valid positive numbers for age, weight, and height."); return; } var bmr; if (gender === 'male') { // Mifflin-St Jeor for Men bmr = (10 * weight) + (6.25 * height) – (5 * age) + 5; } else { // Mifflin-St Jeor for Women bmr = (10 * weight) + (6.25 * height) – (5 * age) – 161; } var tdee = bmr * activity; var weightLoss = tdee – 500; var extremeLoss = tdee – 1000; // Set floors for safety var floor = (gender === 'male') ? 1500 : 1200; document.getElementById('resMaintain').innerText = Math.round(tdee).toLocaleString(); document.getElementById('resLoss').innerText = Math.max(floor, Math.round(weightLoss)).toLocaleString(); document.getElementById('resExtreme').innerText = Math.max(floor, Math.round(extremeLoss)).toLocaleString(); document.getElementById('calResultWrapper').style.display = 'block'; // Smooth scroll to results document.getElementById('calResultWrapper').scrollIntoView({ behavior: 'smooth', block: 'nearest' }); }

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