Intermittent Fasting Calculator
Estimate daily expenditure, fasting-adjusted calorie intake, and projected weekly weight-change pace for popular intermittent fasting protocols.
Low weekly rate. Useful for maintenance-adjacent phases or conservative starts.
| Protocol | Avg kcal/day | %/week |
|---|---|---|
| 14:10 | 2470 | 0.13 |
| 16:8 | 2340 | 0.25 |
| 18:6 | 2262 | 0.33 |
| 20:4 | 2158 | 0.43 |
| OMAD | 2080 | 0.5 |
| 5:2 | 2057 | 0.52 |
Activity assumption: Lightly Active. Light exercise 1-3 days/week.
Projected Weekly Change Pace
Interpretation is based on projected percent body-weight change per week from your intermittent fasting setup.
| RANGE | CATEGORY |
|---|---|
| -1-0 | Weight Gain Average energy intake appears above expenditure in this setup. |
| 0-0.25 | Very Slow Low weekly rate. Useful for maintenance-adjacent phases or conservative starts. |
| 0.25-0.75 | Steady Typical sustainable pace for many adults. |
| 0.75-1 | Brisk Faster but often manageable with adequate protein and recovery. |
| 1-1.50 | Aggressive Aggressive pace. Monitor performance, hunger, and sleep quality closely. |
| 1.50-2 | Very Aggressive High weekly rate with increased lean-mass retention risk. |
| 2+ | Extreme Very high projected pace. Medical supervision is recommended. |
What This Intermittent Fasting Calculator Estimates
This tool estimates your resting energy needs, scales them to daily expenditure (TDEE), then models intake under fasting protocols to project likely weekly body-weight change.
How To Use This for Planning
Use this as a scenario planner: compare protocols, then pick the least aggressive setup you can sustain with stable sleep, training performance, and adherence.
For a day-by-day projection based on fasting vs non-fasting days, compare this with the Fasting Weight Loss Calculator. For non-fasting setups, use the Calorie Deficit Calculator. To estimate real meal intake by photo on feeding days, use the Calorie Estimator. To estimate walking output from your daily step target, add the Steps to Calories Calculator.
Important Assumptions and Limits
Protocol-based intake reduction is an estimate, not a guarantee. Real outcomes vary with appetite compensation, food choices, adherence, and fluid shifts.
If progress stalls, calibrate with 2 to 4 weeks of measured trend data and adjust intake or activity in smaller steps.
For underlying maintenance assumptions, run the TDEE Calculator and BMR Calculator.
References
- Mifflin-St Jeor resting energy equation (PubMed):A New Predictive Equation for Resting Energy Expenditure
- Time-restricted eating trial in adults with overweight/obesity (PubMed):Effect of Time-Restricted Eating on Weight Loss
- Calorie restriction with or without time-restricted eating (PubMed):Calorie Restriction with or without Time-Restricted Eating in Weight Loss
More Tools →
Fasting Weight Loss Calculator
Project weight change from fasting-day and feeding-day calorie patterns.
Weight Loss Calculator
Estimate timeline to target weight with adaptive energy-balance math.
Calorie Deficit Calculator
Calculate deficit targets and daily calories from your selected weekly pace.
Calorie Estimator
Estimate meal calories from a photo with AI and confidence ranges.