Estimate Your Daily Calorie Deficit
Calculate estimated maintenance calories, choose a daily deficit, and see a practical calorie target and approximate weekly weight change.
How the calorie deficit calculator works
A calorie deficit occurs when your energy intake is lower than the energy your body uses. This calculator first estimates basal metabolic rate (BMR) with the Mifflin–St Jeor equation, then multiplies it by your selected activity factor to estimate total daily energy expenditure (TDEE).
The weekly change is a simple energy-equivalent estimate. Actual weight change can differ because energy needs, activity, fluid balance, body composition, and adherence change over time.
Activity factors
| Level | Factor | General description |
|---|---|---|
| Sedentary | 1.20 | Little structured exercise |
| Lightly active | 1.375 | Light exercise 1–3 days weekly |
| Moderately active | 1.55 | Moderate exercise 3–5 days weekly |
| Very active | 1.725 | Hard exercise most days |
| Extra active | 1.90 | Very hard training or a physical job |
Choosing a calorie deficit
A smaller deficit is generally easier to sustain, while a larger deficit may increase hunger, fatigue, and the challenge of meeting nutrient needs. Treat the output as a starting estimate and adjust based on your measured trend over several weeks.
- 250 kcal/day: gradual approach that may be easier to maintain.
- 500 kcal/day: a commonly used moderate planning value.
- 750–1,000 kcal/day: more aggressive and not suitable for everyone; professional guidance is wise.
For a more detailed model that accounts for metabolic adaptation over time, consider the NIDDK Body Weight Planner.
Frequently asked questions
Is a 500-calorie deficit guaranteed to produce the same loss each week?
No. The weekly figure is only a rough planning estimate. Scale weight also reflects water and glycogen, and energy expenditure can change as body weight changes.
What is the difference between BMR and TDEE?
BMR estimates energy used at rest for basic functions. TDEE adds an activity multiplier to estimate total daily energy use.
Should exercise calories be added back?
The activity selection already attempts to include typical activity. Adding all exercise calories again may double-count them, especially because trackers can be imprecise.
How often should I update the calculation?
Recalculate after a meaningful weight or activity change. Compare the estimate with your real trend and make small adjustments rather than reacting to day-to-day fluctuations.