Fit Nutrition library
Intermittent Fasting Calculator
Calorie targets for common fasting windows.
How it’s calculated
Maintenance calories come from Mifflin–St Jeor × activity, adjusted slightly by the protocol; 5:2 is a weekly average.
16:8 = TDEE × 1.0 · 18:6 = × 0.95 · 20:4 = × 0.90. 5:2 = (5 normal days + 2 × 500 kcal) ÷ 7.
Source: TDEE via Mifflin–St Jeor (1990); protocol factors are a practical framework.