Calorie Deficit Calculator
This tool estimates maintenance calories, shows what modest daily deficits of 250 and 500 kcal look like, and gives a rough timeline. It never shows targets below common calorie floors.
Your result
Fill in the form and choose Calculate.
Estimates are educational. They do not diagnose any condition and do not establish eligibility for any medication. A licensed provider decides what is appropriate for you. Explore programs.
How it works
Maintenance = Mifflin-St Jeor resting energy × activity factor. Targets = maintenance − 250 and − 500 kcal. The timeline uses the traditional 3,500 kcal per pound rule.
Guardrails
Targets below 1,200 kcal a day (female constant) or 1,500 kcal a day (male constant) are never shown; the NHLBI Practical Guide treats lower intakes as needing medical supervision.
Limitations
- The 3,500 kcal rule overstates long-term loss because energy needs fall as weight falls (Thomas 2013). The NIDDK Body Weight Planner gives a more realistic projection.
- It does not account for medications, including GLP-1 medications that reduce appetite.
Sources
- Mifflin MD et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr 1990
- Thomas DM et al. Can a weight loss of one pound a week be achieved with a 3500-kcal deficit? Int J Obes 2013
- Body Weight Planner | NIDDK
- The Practical Guide: Identification, Evaluation, and Treatment of Overweight and Obesity in Adults | NHLBI
Calorie Deficit Calculator
questions
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Why only 250 and 500 kcal?
Modest deficits are easier to sustain and help preserve lean mass.
Is a pound a week realistic?
At first, often. Over time loss slows as energy needs fall, so the timeline is a rough scenario.