Your Starting Point
Deficit: 500 calories/day
How It Works
This calculator projects your weight loss timeline using established metabolic equations. Here is the math behind the projection:
Step 1: Calculate Your BMR
We use the Mifflin-St Jeor equation, which research shows is more accurate than the older Harris-Benedict formula for modern populations:
Women: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161
Step 2: Apply Activity Multiplier
Your BMR is multiplied by an activity factor to get your Total Daily Energy Expenditure (TDEE):
- Sedentary (1.2): Desk job, little to no exercise
- Lightly Active (1.375): Light exercise 1–3 days/week
- Moderately Active (1.55): Moderate exercise 3–5 days/week
- Very Active (1.725): Hard exercise 6–7 days/week
- Extremely Active (1.9): Physical job + hard training
Step 3: Model the Deficit
A pound of fat contains approximately 3,500 calories. To lose 1 lb per week, you need a daily deficit of 500 calories. The timeline is calculated as:
Metabolic Adaptation
As you lose weight, your BMR drops slightly because there is less body mass to maintain. The calculator applies a 5% metabolic adaptation factor to keep projections realistic. Very aggressive deficits (750+ cal/day) may trigger stronger adaptation and are harder to sustain.
Practical Tips
- The "Moderate" scenario (500 cal/day deficit) is sustainable for most people and yields ~1 lb/week loss.
- Aggressive deficits work short-term but increase muscle loss and rebound risk.
- Save multiple scenarios to compare approaches. All data stays in your browser.
- Plateaus are normal. If your weight stalls for 2+ weeks, recalculate with your new weight and adjust the deficit.
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