Calorie Deficit Guide: Complete Explanation of BMR, TDEE, and Weight Loss

Learn what a calorie deficit is, how to calculate your BMR and TDEE, and how to create a safe, effective weight loss plan.

What is a Calorie Deficit?

A calorie deficit occurs when you consume fewer calories than your body burns in a day. This forces your body to use stored energy (fat and sometimes muscle) for fuel, leading to weight loss over time. The size of the deficit determines the rate of weight loss.

How Calorie Deficit Works

Your body requires energy for all its functions, from breathing to physical activity. The total energy you burn daily is called Total Daily Energy Expenditure (TDEE). If you eat less than TDEE, you create a deficit. If you eat more, you create a surplus and gain weight.

Understanding BMR (Basal Metabolic Rate)

BMR is the number of calories your body burns at complete rest to maintain vital functions. It accounts for 60–70% of your total energy expenditure. Our calculator uses the Mifflin-St Jeor equation, which is widely accepted for estimating BMR.

Mifflin-St Jeor Equation

For men: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) + 5

For women: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) − 161

What is TDEE?

TDEE is your total daily energy expenditure, calculated by multiplying your BMR by an activity factor. Activity factors range from 1.20 (sedentary) to 1.90 (extra active). For example, a moderately active person uses a multiplier of 1.55.

How to Calculate Your Calorie Deficit

Subtract 250–500 calories from your TDEE to create a moderate deficit. This typically results in 0.25–0.5 kg of weight loss per week. Our calculator does this automatically and provides a safe target.

Setting Realistic Weight Loss Goals

Aim to lose 0.5–1% of your body weight per week. For a 70 kg person, that's 0.35–0.7 kg/week. Rapid weight loss is often unsustainable and can lead to muscle loss and metabolic slowdown.

Common Mistakes to Avoid

• Eating too few calories (below BMR)
• Ignoring protein intake
• Not tracking accurately
• Overestimating exercise calories
• Not adjusting after weight loss

Scientific Limitations

Predictive formulas are estimates based on population averages. Individual energy needs can vary by 10–20% or more due to genetics, body composition, and metabolic adaptation. Always monitor your progress and adjust accordingly.

Use our Calorie Deficit Calculator to get your personalized estimate.