BMR Calculator Online.

WEIGHT LOSS SCIENCE

BMR Calculator to Lose Weight.

Losing fat without regaining it requires understanding the mathematical relationship between your resting energy expenditure (BMR) and your total daily burn (TDEE). Here is the evidence-based protocol to drop body fat sustainably.

Find your personal fat loss calorie target

Use our live calculator to find your BMR and your maintenance calories across 6 activity levels.

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Essential Weight Loss Rules

Step-by-Step: How to Calculate Your Weight Loss Calories

Follow these 4 verified steps to pinpoint your exact daily food intake for fat loss:

  1. Step 1: Calculate your BMR
    Using the Mifflin–St Jeor formula on our homepage, enter your age, sex, height, and weight. For example, a 35-year-old female weighing 75 kg at 165 cm has a BMR of approximately 1,445 kcal.
  2. Step 2: Identify your true activity level (TDEE)
    Multiply your BMR by your weekly physical activity factor:
    • Sedentary (desk job, minimal movement): BMR × 1.2 = 1,734 kcal
    • Light exercise (1–3 days/week): BMR × 1.375 = 1,987 kcal
    • Moderate exercise (3–5 days/week): BMR × 1.55 = 2,240 kcal
  3. Step 3: Deduct a sustainable calorie deficit
    Subtract 300 to 500 calories from your TDEE. If your TDEE is 1,987 kcal, your fat loss intake is: 1,987 - 500 = 1,487 kcal per day.
  4. Step 4: Check against your BMR baseline
    Confirm your final target (1,487 kcal) is at or slightly above your resting BMR (1,445 kcal). This ensures healthy organ function, restful sleep, and steady hormone regulation while remaining in a genuine energy deficit.

Daily Calorie Target Matrix for Fat Loss

Resting BMRSedentary TDEEModerate TDEESafe Weight Loss Target (500 kcal Deficit)
1,300 kcal1,560 kcal2,015 kcal1,300 – 1,515 kcal/day
1,500 kcal1,800 kcal2,325 kcal1,500 – 1,825 kcal/day
1,700 kcal2,040 kcal2,635 kcal1,650 – 2,135 kcal/day
1,900 kcal2,280 kcal2,945 kcal1,850 – 2,445 kcal/day
2,100 kcal2,520 kcal3,255 kcal2,050 – 2,755 kcal/day

Why "Starvation Diets" Destroy Your Metabolism

When people follow crash diets (e.g. eating 800–1,000 calories daily), initial scale weight drops rapidly because glycogen and water are lost alongside muscle tissue. However, the body senses severe starvation and initiates several defense mechanisms:

By contrast, eating at a mild deficit just above your BMR with adequate protein guarantees that virtually all lost weight is adipose body fat rather than lean tissue.

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Get your scientific BMR and maintenance calories on our instant online calculator.

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