A calorie deficit means taking in less energy than you use, so the body draws on stored fat. This calculator estimates your maintenance calories with the Mifflin-St Jeor equation and an activity factor, then shows what modest daily deficits of 250 and 500 kcal would look like, along with a rough timeline to your goal weight. It applies common calorie floors and will explain when a deficit is not suitable to show.
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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 treatments if you want to learn about provider-guided programs.
Your approximate maintenance calories, two illustrative intake targets built on modest deficits, and a rough timeline to a goal weight. The purpose is to show the scale of the numbers, not to assign a diet.
Step 1: resting energy expenditure with Mifflin-St Jeor.
Men: REE = 10 × kg + 6.25 × cm − 5 × age + 5Women: REE = 10 × kg + 6.25 × cm − 5 × age − 161
Step 2: maintenance (TDEE) = REE × activity factor (1.2, 1.375, 1.55, 1.725 or 1.9).
Step 3: illustrative targets = maintenance − 250 and maintenance − 500 kcal per day.
Step 4: rough timeline using the traditional rule that 3,500 kcal corresponds to about one pound of body fat, so a 500 kcal daily deficit is about 1 lb per week and 250 kcal about 0.5 lb per week:
weeks ≈ pounds to lose ÷ (daily deficit × 7 ÷ 3,500)
Modest deficits are easier to sustain, preserve more lean mass and are the range most guidance treats as a reasonable starting point. Larger deficits increase the chance of nutrient shortfalls and muscle loss and are generally reserved for supervised programs.
Those are common floors used in guidance for women and men without medical supervision. Below them it becomes hard to meet protein and micronutrient needs from food. If your estimate falls there, a licensed provider or registered dietitian can build a plan that fits your situation.
At first, often yes with a 500 kcal deficit. Over time, energy needs fall as weight drops, so the same intake produces a smaller deficit and loss slows. The 3,500 kcal rule does not capture this, which is why the timeline is labeled a rough scenario.
Appetite-reducing medications change how much you naturally eat, and intake can fall faster than planned. Protein and hydration still matter. Follow the guidance of the licensed provider managing your prescription rather than a generic deficit.
Plateaus are normal. Lower body weight means lower energy needs, water retention can mask fat loss for weeks, and intake estimates drift. Re-estimating maintenance at your new weight and reviewing tracking accuracy usually explains it.
No, this tool is only for a deficit toward a lower goal weight. The TDEE calculator gives your maintenance estimate, which is the right starting point for maintenance or a modest surplus.
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