How This Calorie Deficit Calculator Works
This tool starts by estimating your maintenance calories (TDEE) using your age, sex, height, weight, and activity level. From there, it maps your chosen weekly fat loss target to a daily calorie deficit and projects how long it might take to reach your goal weight.
The Math Behind the Estimates
Your Basal Metabolic Rate (BMR) is calculated with the Mifflin–St Jeor equation — a widely used formula for active adults. We then multiply BMR by an activity factor to estimate your Total Daily Energy Expenditure (TDEE), or how many calories you burn on an average day.
To connect calories to fat loss, the calculator uses the rough rule of ≈ 7,700 kcal per kg of body weight. Your weekly fat loss target sets how large your weekly and daily calorie deficit needs to be.
Choosing a Sustainable Weekly Loss Target
- 0.25–0.5 kg/week: Very sustainable, best for long cuts or leaner individuals.
- 0.5–0.8 kg/week: Great balance between speed and adherence for most people.
- 0.8–1.0+ kg/week: Aggressive — use short term and monitor performance, mood, and hunger closely.
What to Do If You Hit a Plateau
- Confirm tracking: weigh food for a week and verify your step count.
- Increase daily movement: add 2,000–3,000 steps per day.
- Reduce calories slightly: drop 100–150 kcal/day and reassess for 2 weeks.
- Keep protein high and strength train 2–4x/week to protect muscle.
Combine This With Other PhysiqueFormulas Tools
Once you have a daily calorie target, use the Macro Calculator to break those calories into protein, carbs, and fats, or fine-tune your TDEE if your activity changes.