Low Carb Diet Calculator

Low Carb Diet Macro Calculator

Use this calculator to estimate your daily calorie and macronutrient (carbohydrate, protein, fat) needs for a low-carb diet. Whether you're aiming for a ketogenic, moderate, or liberal low-carb approach, this tool will help you set your targets based on your personal data and activity level.

function calculateLowCarbMacros() { var currentWeightLbs = parseFloat(document.getElementById("currentWeight").value); var heightInches = parseFloat(document.getElementById("heightInches").value); var ageYears = parseFloat(document.getElementById("ageYears").value); var gender = document.querySelector('input[name="gender"]:checked').value; var activityLevel = document.getElementById("activityLevel").value; var lowCarbGoal = document.getElementById("lowCarbGoal").value; var weightGoal = document.getElementById("weightGoal").value; var resultDiv = document.getElementById("result"); resultDiv.innerHTML = ""; // Clear previous results // Input validation if (isNaN(currentWeightLbs) || isNaN(heightInches) || isNaN(ageYears) || currentWeightLbs <= 0 || heightInches <= 0 || ageYears <= 0) { resultDiv.innerHTML = "Please enter valid positive numbers for all fields."; return; } // Convert to metric for BMR calculation var weightKg = currentWeightLbs / 2.20462; var heightCm = heightInches * 2.54; // 1. Calculate Basal Metabolic Rate (BMR) – Mifflin-St Jeor Equation var bmr; if (gender === 'male') { bmr = (10 * weightKg) + (6.25 * heightCm) – (5 * ageYears) + 5; } else { // female bmr = (10 * weightKg) + (6.25 * heightCm) – (5 * ageYears) – 161; } // 2. Calculate Total Daily Energy Expenditure (TDEE) 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 'extremelyActive': activityFactor = 1.9; break; default: activityFactor = 1.2; // Default to sedentary } var tdee = bmr * activityFactor; // 3. Adjust TDEE for Weight Goal var targetCalories = tdee; switch (weightGoal) { case 'maintain': // No change break; case 'mildLoss': targetCalories -= 250; break; case 'moderateLoss': targetCalories -= 500; break; case 'aggressiveLoss': targetCalories -= 750; break; case 'mildGain': targetCalories += 250; break; case 'moderateGain': targetCalories += 500; break; } // Ensure target calories don't go below a healthy minimum var minCalories = (gender === 'female') ? 1200 : 1500; if (targetCalories < minCalories) { resultDiv.innerHTML += "Note: Your calculated calorie target was below the recommended minimum for health. It has been adjusted from " + Math.round(targetCalories) + " to " + minCalories + " calories."; targetCalories = minCalories; } // 4. Calculate Macronutrient Split var proteinGrams, carbGrams, fatGrams; var proteinCalories, carbCalories, fatCalories; // Protein: Generally 0.8g to 1.0g per pound of current body weight for low-carb proteinGrams = currentWeightLbs * 0.9; // Using an average of 0.9g/lb proteinCalories = proteinGrams * 4; // Carbs: Based on lowCarbGoal switch (lowCarbGoal) { case 'ketogenic': carbGrams = 30; // Fixed 30g net carbs for keto break; case 'moderate': carbGrams = 75; // Fixed 75g net carbs for moderate low carb break; case 'liberal': carbGrams = 125; // Fixed 125g net carbs for liberal low carb break; default: carbGrams = 30; } carbCalories = carbGrams * 4; // Fat: Remaining calories var remainingCaloriesForFat = targetCalories – proteinCalories – carbCalories; if (remainingCaloriesForFat < 0) { // This can happen if protein/carb targets are too high for a very low calorie goal. // Adjust fat to 0 and warn the user. fatGrams = 0; resultDiv.innerHTML += "Warning: Your protein and carb targets exceed your total calorie goal. Fat grams have been set to 0. You may need to adjust your weight loss goal or macro targets."; } else { fatGrams = remainingCaloriesForFat / 9; } fatCalories = fatGrams * 9; // Display Results resultDiv.innerHTML += "

Your Daily Low Carb Macro Targets:

"; resultDiv.innerHTML += "Target Calories: " + Math.round(targetCalories) + " kcal"; resultDiv.innerHTML += "

"; resultDiv.innerHTML += "
• Carbohydrates: " + Math.round(carbGrams) + "g (" + Math.round((carbCalories / targetCalories) * 100) + "%)
"; resultDiv.innerHTML += "
• Protein: " + Math.round(proteinGrams) + "g (" + Math.round((proteinCalories / targetCalories) * 100) + "%)
"; resultDiv.innerHTML += "
• Fat: " + Math.round(fatGrams) + "g (" + Math.round((fatCalories / targetCalories) * 100) + "%)
"; resultDiv.innerHTML += "

"; resultDiv.innerHTML += "These are estimates. Individual needs may vary. Consult a healthcare professional or registered dietitian for personalized advice."; }

Understanding Your Low Carb Diet

A low-carb diet emphasizes reducing carbohydrate intake, typically focusing on protein and healthy fats. The specific definition of "low-carb" can vary, ranging from very strict ketogenic diets to more liberal approaches. The goal is often to shift the body's metabolism from burning carbohydrates for energy to burning fat, a state known as ketosis in its most extreme form.

Benefits of a Low Carb Diet:

• Weight Loss: Many find low-carb diets effective for weight loss due to reduced appetite, increased satiety from protein and fat, and the body's increased fat-burning capabilities.
• Blood Sugar Control: By limiting carbohydrates, low-carb diets can significantly help stabilize blood sugar levels, making them beneficial for individuals with type 2 diabetes or insulin resistance.
• Improved Cholesterol Markers: While often debated, some studies show improvements in HDL (good) cholesterol and triglyceride levels on low-carb diets.
• Reduced Cravings: Stable blood sugar can lead to fewer cravings and less energy crashes throughout the day.

How This Calculator Works:

This calculator uses established scientific formulas to estimate your daily energy needs and then allocates macronutrients based on common low-carb guidelines:

1. Basal Metabolic Rate (BMR): This is the number of calories your body burns at rest to maintain basic bodily functions. We use the Mifflin-St Jeor equation, which is widely accepted as accurate.
2. Total Daily Energy Expenditure (TDEE): Your BMR is multiplied by an activity factor to estimate the total calories you burn in a day, accounting for your exercise and daily movement.
3. Calorie Adjustment for Goals: Your TDEE is then adjusted based on your weight goal (e.g., a deficit for weight loss, a surplus for weight gain).
4. Macronutrient Split:
   • Protein: Calculated based on your current body weight to support muscle maintenance and satiety.
   • Carbohydrates: Set according to your chosen low-carb goal (Ketogenic, Moderate, or Liberal).
   • Fat: The remaining calories are allocated to fat, which is crucial for energy, hormone production, and nutrient absorption on a low-carb diet.

Important Considerations:

While this calculator provides a great starting point, individual results may vary. Factors like body composition, metabolic health, and specific dietary preferences can influence your ideal macro targets. Always listen to your body and consider consulting with a healthcare professional or a registered dietitian before making significant dietary changes, especially if you have underlying health conditions.