Calorie Deficit Calculator
Calculate your TDEE and daily calorie target for weight loss, maintenance, or muscle gain.
Your Details
Your Calorie Targets
Based on the Mifflin–St Jeor equation. These are estimates — adjust based on real-world results over 2–3 weeks.
Fill in your details above to see your calorie targets.
Frequently Asked Questions
What is a calorie deficit and how does it cause fat loss?
A calorie deficit means consuming fewer calories than your body burns in a day. When this happens, your body turns to stored energy — primarily body fat — to make up the shortfall. One kilogram of body fat stores roughly 7,700 kilocalories, so a daily deficit of 500 kcal produces approximately 0.5 kg of fat loss per week in theory.
In practice, real-world weight loss is messier. Water retention fluctuates, muscle can be gained or lost simultaneously, and your body adapts over time by reducing TDEE as you lose weight. This is why the calculator's output is a starting estimate, not a permanent prescription — you should reassess every 4–6 weeks as your weight changes.
The key principle is that fat loss requires a sustained energy deficit, but the size of that deficit involves trade-offs. Larger deficits lead to faster weight loss on the scale but also greater muscle loss, hormonal disruption, and diet fatigue. Most evidence supports moderate deficits (300–500 kcal) as the sweet spot for long-term success.
BMR vs TDEE — what's the difference?
Basal Metabolic Rate (BMR)
The number of calories your body needs to maintain basic functions — breathing, circulation, cell repair — while completely at rest. Think of it as your body's idle engine speed. It accounts for 60–75% of most people's total calorie burn.
Total Daily Energy Expenditure (TDEE)
BMR multiplied by an activity factor that accounts for all movement — exercise, walking, fidgeting (NEAT), and digesting food (TEF). TDEE is the actual number of calories you burn each day and the baseline for calculating your deficit or surplus.
This calculator uses the Mifflin–St Jeor equation to estimate BMR, which a 2005 meta-analysis in the Journal of the American Dietetic Association found to be the most accurate BMR formula for most adults, within about 10% of measured values.
Calorie targets by goal — a practical guide
| Goal | Deficit / Surplus | Expected rate | Best for |
|---|---|---|---|
| Aggressive cut | −750 kcal | ~0.75 kg/week | Short-term, disciplined dieters |
| Moderate cut | −500 kcal | ~0.5 kg/week | Most people — sustainable |
| Mild cut | −250 kcal | ~0.25 kg/week | Simultaneous muscle gain |
| Maintenance | 0 kcal | Weight stable | Body recomposition / breaks |
| Lean bulk | +250–300 kcal | +0.1–0.2 kg/week | Muscle gain with minimal fat |
Why your results may differ from the calculator
Activity level is overestimated
Most people select "moderately active" when they are closer to "lightly active." If you are losing slower than expected, try dropping one activity level before cutting calories further.
Calorie tracking error
Studies consistently show people underestimate food intake by 20–40%. Cooking oils, sauces, and "small bites" add up. Weigh food with a kitchen scale for 1–2 weeks to calibrate your intuition.
Metabolic adaptation
As you lose weight, your TDEE drops — you are carrying less mass and your body becomes more efficient. Recalculate every 4–6 weeks using your new weight.
Sleep and stress
Poor sleep and chronic stress elevate cortisol, which promotes fat storage and increases appetite. You can be in a theoretical deficit but still not lose fat if these factors are not managed.