What this tool does
This calorie deficit calculator estimates TDEE from your body stats and activity, subtracts your chosen percent (10–25%), and reports the daily calorie target, the gap below maintenance, and a rough weekly kilogram change. If the cut would land under the educational floor, intake is raised and flagged.
How it works
Enter sex, age, height, weight, and activity. The tool runs Mifflin-St Jeor BMR, multiplies by an activity factor for TDEE, then applies target = TDEE × (1 − deficit%). Weekly change ≈ daily gap × 7 ÷ 7,700. Hall’s work is why that weekly figure stays labeled rough — adaptation and mixed tissue loss mean the scale will not obey a straight line.
Formula and methodology
TDEE = Mifflin-St Jeor BMR × activity. Target = TDEE × (1 − deficit%/100), floored at 1,200 kcal (female) or 1,500 kcal (male). Rough kg/week ≈ (TDEE − target) ÷ (7,700/7). The 7,700 kcal/kg (≈3,500 kcal/lb) rule is a classroom shortcut, not a contract.
How to interpret the result
A 10% cut is a nudge. A 15–20% band is the usual sustainable neighborhood. A 25% cut is aggressive and more likely to wreck training and NEAT. If the floor triggered, you asked for more deficit than this page will print. Pair the target with protein in the deficit band on the protein calculator.
Example
Worked example: 80 kg, 175 cm, age 35, male, lightly active → Mifflin-St Jeor TDEE ≈ 2,760 kcal. A 20% deficit → target ≈ 2,210 kcal, gap ≈ 550 kcal/day, very roughly 0.5 kg/week on paper. Real weeks wander with sodium, glycogen, and menstrual cycle. Two weeks of averages beat any single Wednesday.
Common mistakes
- Subtracting a flat 500 kcal without knowing TDEE — a percent scales with your maintenance.
- Stacking a 25% food cut on top of a new 12,000-step habit that was not in TDEE — double counting the gap.
- Dropping another 300 kcal the first time the scale holds water.
- Ignoring protein and losing more performance than fat.
- Using the weekly kg line as a bet you must “win.”
When this estimate may be off
- Activity was overstated, so TDEE was fantasy.
- You already lost a lot of weight and the old TDEE is stale.
- Medications, edema, or cycle-related water swamp the weekly signal.
- Intake logging misses oils and weekend alcohol.