How Many Calories Should You Eat? TDEE & Weight Loss

Mifflin-St Jeor: BMR × Activity Factor

Variables Explained

Deficits, Plateaus & Refeeds

• 1Worked example: a 40-year-old woman at 65 kg / 163 cm has BMR = 1,308; × 1.55 for moderate activity = 2,027 maintenance, so eating 1,527 targets a 1-lb/week cut.
• 2A calorie target is only useful if it is grounded in your real maintenance needs — eating 1,800 calories a day either cuts weight or causes gain depending on whether your maintenance is 1,600 or 2,200.
• 3Protein is the most satiating macronutrient. Aim for 25-30g of protein per meal when in a calorie deficit to help preserve muscle mass and control hunger.
• 4Not all calories are equal in how they affect your body. Whole foods like vegetables, lean proteins, and whole grains require more energy to digest than processed foods.
• 5Tracking your food intake with a food scale is significantly more accurate than estimating portion sizes. Studies show people typically underestimate their calorie intake by 30-50%.
• 6Your TDEE changes as you lose weight. A lighter body requires fewer calories, so your calorie deficit naturally shrinks over time. Recalculate your TDEE every 5-10 kg lost.

Energy Balance Vocabulary

BMR

Basal Metabolic Rate — the minimum energy your body needs at complete rest to maintain vital functions like breathing and circulation.

TDEE

Total Daily Energy Expenditure — the total number of calories burned per day, combining BMR with physical activity and digestion.

Calorie Deficit

Eating fewer calories than your TDEE, resulting in weight loss. A 500-calorie daily deficit produces approximately 0.5 kg of fat loss per week.

Thermic Effect of Food (TEF)

Energy required to digest and process nutrients. TEF accounts for ~10% of daily calorie expenditure.

Clinical Nutrition & NIH Sources

Our calculations are based on established financial and scientific formulas. The following sources inform the default values and methodology used in this calculator:

• Mifflin MD, St Jeor ST, et al. — A new predictive equation for resting metabolic rate (1990)
• National Institutes of Health (NIH) — Body weight planner
• U.S. Department of Agriculture (USDA) — Dietary Guidelines for Americans

How Many Calories Do You Need Daily?

Your daily calorie needs are determined by your Basal Metabolic Rate (BMR) and your activity level. The Mifflin-St Jeor formula is the gold standard for estimating BMR. Once you know your BMR, multiply by an activity factor to get your Total Daily Energy Expenditure (TDEE), then adjust based on your goal — weight loss, maintenance, or muscle gain.

Men: BMR = 10 × weight(kg) + 6.25 × height(cm) - 5 × age + 5
Women: BMR = 10 × weight(kg) + 6.25 × height(cm) - 5 × age - 161

Example: A 30-year-old woman, 165 cm, 65 kg:
BMR = 10 × 65 + 6.25 × 165 - 5 × 30 - 161 = 1,370 kcal
With moderate exercise (1.55): TDEE = 1,370 × 1.55 = 2,124 kcal
For weight loss: 2,124 - 400 = 1,724 kcal/day

Calorie Management Tips

• •Use a food tracking app for 2-3 weeks to understand your baseline intake
• •Prioritize protein (1.6-2.2g per kg of body weight) regardless of your goal
• •Don't eat below your BMR — it slows metabolism and causes muscle loss
• •Adjust calories gradually: change by 100-200 kcal at a time, wait 2 weeks
• •Track your weight weekly at the same time of day for consistent data

The most effective calorie management strategy is one you can sustain long-term. A moderate deficit of 300-500 kcal below TDEE allows for steady weight loss without triggering metabolic adaptation. Pair your calorie target with strength training to preserve muscle mass during weight loss.

TDEE and Calorie Deficit: Your Weight Loss Blueprint

Understanding your Total Daily Energy Expenditure (TDEE) is the key to successful weight loss. Below we show how different calorie deficits translate to weight loss over 3 months for a person with a TDEE of 2,200 calories.

A moderate deficit of 500 calories below TDEE is the sweet spot — sustainable enough to maintain long-term while losing 1 lb per week. Never eat below your BMR (typically 1,200-1,500 calories for most adults) without medical supervision, as it can slow metabolism and cause muscle loss.

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