| Daily Deficit | Calorie Target | Simple Weekly Equivalent* |
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How a Calorie Deficit Works
A calorie deficit means average energy intake is below average energy expenditure. Your maintenance calories, often called Total Daily Energy Expenditure (TDEE), are an estimate of the calories used across daily life and activity.
CDC notes that gradual, steady weight loss of about 1 to 2 pounds per week is more likely to be maintained than faster loss. That is population-level guidance, not a personalized prescription. Medicines, medical conditions, hormones, age, stress and other factors can affect weight management.
How TDEE Is Estimated Here
If you choose Estimate My TDEE, the calculator first estimates Basal Metabolic Rate (BMR) using the Mifflin-St Jeor equation, then multiplies it by the activity factor you select. Activity multipliers are approximations, so the result is best treated as a starting estimate rather than a measured metabolism.
If you already know your TDEE from tracking or another source, use I Know My TDEE. This avoids forcing you to recalculate maintenance calories from generic activity categories.
Calorie Deficit FAQ
What calorie deficit should I use?
There is no single deficit that is appropriate for every adult. The calculator lets you compare several deficits instead of declaring one universally “best.” CDC describes gradual weight loss of about 1–2 lb per week as a general pattern associated with better maintenance, while individual needs can differ.
Is a 500-calorie deficit exactly 1 pound per week?
No. The traditional arithmetic gives a simple estimate near 1 lb per week, but real body-weight change is dynamic. NIH research notes that metabolism and energy expenditure adapt as weight changes, so long-term loss is not perfectly linear.
Why does my real weight loss differ from the calculator?
TDEE itself is an estimate and can change. Food tracking error, activity, body composition, medications, health conditions, fluid changes and metabolic adaptation can all make real results differ from a mathematical estimate.
Can I use this during pregnancy or breastfeeding?
No. This calculator is intentionally designed for nonpregnant, nonbreastfeeding adults age 18 and older. NIH's Body Weight Planner uses the same adult-only exclusion for its planning tool.
Should I eat below 1,200 calories?
This calculator does not automatically prescribe a minimum intake. NIDDK materials for a Diabetes Prevention Program state that eating below 1,200 calories per day is not advised in that program. Individual calorie needs can vary, so very low targets should be discussed with an appropriate health professional rather than generated automatically by a general calculator.
Sources: NIH/NIDDK Body Weight Planner, NIDDK research behind the planner, and CDC Steps for Losing Weight.