Calorie Deficit Calculator

What the Calorie Deficit Calculator does

This calculator estimates how many calories a day you would eat to reach a weight goal. You enter age, height, weight, an activity level, and a target pace (maintain, or lose about half a pound to a pound and a half per week), and it returns three numbers: your resting metabolic rate, your maintenance calories, and the daily target that creates your chosen deficit.

If your target falls below 1,200 calories a day, it flags that very low intakes generally need medical supervision. All math runs in your browser.

How to read your result

The target calorie number is a starting estimate, not a prescription. Real energy needs vary with genetics, body composition, and non-exercise movement, so use it as a baseline to adjust from based on real-world results over a few weeks.

The resting-rate and maintenance figures explain where the target comes from: maintenance is what holds your weight steady, and the target subtracts a fixed deficit from it.

What the result is based on

Resting metabolic rate uses the Mifflin-St Jeor equation for women. Maintenance calories multiply that by an activity factor from 1.2 (sedentary) to 1.725 (very active). The weight-loss targets subtract 250, 500, or 750 calories a day, which correspond to roughly half a pound, one pound, and one and a half pounds of loss per week.

The calculator uses the female form of the equation and applies no other personalization.

What it cannot tell you

• The Mifflin-St Jeor equation is a population estimate; your actual metabolism can differ by a few hundred calories.
• Activity factors are broad buckets and cannot capture your real daily movement.
• It does not account for medical conditions, medications, pregnancy, or breastfeeding, all of which change energy needs.
• Weight loss is not perfectly linear, and the 3,500-calories-per-pound rule the pace targets rely on is an approximation.
• It does not tell you what to eat or ensure a target is nutritionally adequate.