Intermittent Fasting Calculator
Enter your stats to get personalized eating window times, daily calorie targets, and macro breakdowns for your chosen IF protocol.
Metabolic Breakdown
Macro Calorie Distribution
Pair this calculator with PlateLens
Your calculated targets only work if your daily tracking is accurate. PlateLens identifies every ingredient from a photo — within ±1.2% of actual calories — so you know exactly where you stand in your eating window.
How This Calculator Works
This calculator uses the Mifflin-St Jeor formula — the most validated BMR equation for general populations — combined with your activity multiplier to estimate your Total Daily Energy Expenditure (TDEE).
The Calculations
BMR (Men): (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5
BMR (Women): (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161
TDEE = BMR × Activity Multiplier
Target Calories = TDEE ± Goal Adjustment
Macro Allocation
Protein is set at 1.8g per kg of body weight — the evidence-based target for muscle preservation during fasting-based weight loss. Fat is set at 0.8g per kg. Remaining calories are allocated to carbohydrates.
Accuracy Disclaimer
BMR formulas carry ±10–15% individual variability. These targets are your starting point. Adjust based on 2-week results. If weight loss is faster than expected, add 100–200 calories primarily from carbohydrates. If stalled, reduce by 100–200 calories.
This calculator is designed specifically for intermittent fasting protocols. For a general-purpose TDEE and calorie calculator that also covers non-fasting approaches and includes a separate macro calculator, the free tool at my-calorie-calculator.com offers a complementary set of calculators built on the same Mifflin-St Jeor methodology.