Calorie Deficit & Diet Calculator

How to Use the Calorie Deficit & Diet Calculator

Enter body stats and activity, choose lose/maintain/gain with an optional pace, then review BMR, TDEE, diet target, weekly change estimate, and simple macros. Estimates only — not medical advice.

1. Choose metric or imperial units.
2. Enter age in years (15–100), sex, height, and weight.
3. Select an activity level.
4. Choose a goal: Lose weight, Maintain weight, or Gain weight.
5. If losing or gaining, choose a pace (Mild, Moderate, or Faster).
6. Press Calculate and review BMR, maintenance (TDEE), diet target, daily deficit/surplus, weekly change, and macros.

Methodology

BMR uses Mifflin–St Jeor. Maintenance (TDEE) = BMR × activity factor. Lose/gain goals apply mild/moderate/faster kcal adjustments; weight-loss targets are raised if they would fall below the tool’s internal calorie floor. Weekly change uses ~7700 kcal ≈ 1 kg as a planning rule of thumb.

Common mistakes

• Overestimating activity level and setting an unrealistically large deficit.
• Treating macros or weekly change as guaranteed outcomes.
• Ignoring the safety floor notice when a faster loss pace is raised to the minimum.

Limitations

For generally healthy adults ages 15–100. Not for pregnancy, eating disorders, or clinical nutrition therapy. Safety floors are product defaults, not universal medical minima. Estimates only — not medical advice.

Privacy

Inputs stay in your browser. Age, height, weight, and goals are not uploaded to ToolsLibrary servers for this calculator.

FAQ

What is a calorie deficit?

A calorie deficit means eating fewer calories than your estimated maintenance (TDEE). Over time that gap is associated with weight loss for many people — but pace, hormones, medication, and health conditions all matter. This tool’s numbers are planning estimates only.

How does this calorie deficit calculator work?

It estimates BMR with the Mifflin–St Jeor equation, multiplies by an activity factor for TDEE/maintenance, then applies a mild, moderate, or faster adjustment for lose or gain goals (or keeps maintenance). A configured calorie floor can raise very low weight-loss targets.

What is BMR?

BMR (basal / resting metabolic rate here) is the Mifflin–St Jeor estimate of calories burned at rest from age, sex, height, and weight. It is rounded to whole kcal/day.

What are maintenance calories?

Maintenance calories (TDEE in this tool) are an estimate of how many calories you burn in a typical day — enough to roughly hold weight if intake matched that number. They are not an exact daily requirement.

What is TDEE?

TDEE means Total Daily Energy Expenditure — estimated total calories burned per day including activity. Here it is shown as maintenance calories: BMR × activity factor.

What activity levels does the calculator use?

Sedentary (1.2), light (1.375), moderate (1.55), active (1.725), and very active (1.9). Higher activity raises estimated TDEE.

Can this calculator estimate calories for weight gain?

Yes. Choose Gain weight and a pace (250, 500, or 750 kcal/day above TDEE) to estimate a calorie surplus target. Results remain planning estimates, not guaranteed gain.

What is the calorie safety floor?

For weight-loss goals, the calculator will not set a diet target below its internal minima: 1500 kcal/day (male), 1200 (female), or 1350 (other). Those are product safety floors for this tool, not universal medical minimums.

Are the results exact?

No. BMR, TDEE, weekly change (using ~7700 kcal ≈ 1 kg as a planning rule), and macros are estimates. Real-world needs and weight change vary between people.

How are macros calculated?

Protein uses about 2.0 / 1.6 / 1.8 g per kg for lose / maintain / gain (capped at 40% of target calories), fat about 25% of target calories, and carbohydrates fill the rest (4 / 4 / 9 kcal per gram). These are meal-planning defaults, not medical prescriptions.

Is my data uploaded?

No. Calculations run in your browser. Age, height, weight, and other inputs are not uploaded to ToolsLibrary servers for this tool.