Calories, TDEE and Macros: The Basics (With Caveats)

Your daily energy expenditure is often described as three parts. Basal metabolic rate (BMR) is the energy used at rest to keep your body running. The thermic effect of food is the energy used to digest and absorb what you eat. Activity energy covers both deliberate exercise and everyday movement. Total daily energy expenditure (TDEE) is the sum. Calculators estimate BMR first and then multiply by an activity factor to approximate TDEE.

This published equation uses weight in kilograms, height in centimetres and age in years:

men: BMR = 10 × weight + 6.25 × height − 5 × age + 5

women: BMR = 10 × weight + 6.25 × height − 5 × age − 161

Example: a 30-year-old woman who weighs 65 kg and is 165 cm tall. BMR = 650 + 1,031.25 − 150 − 161 = 1,370.25 kcal a day.

Example: a 35-year-old man who weighs 80 kg and is 180 cm tall. BMR = 800 + 1,125 − 175 + 5 = 1,755 kcal a day.

These are averages. Individuals can differ by a few hundred calories from the equation’s prediction.

TDEE is BMR times an activity factor. Commonly used values are:

For the woman above, a lightly active multiplier gives 1,370.25 × 1.375 ≈ 1,884 kcal a day; moderately active gives about 2,124. The category choice is the biggest source of error, and most people overestimate their activity. If you are unsure, start with the lower level.

Roughly, eating below TDEE leads to weight loss over time and eating above it leads to gain. A common rule of thumb says a pound of body fat corresponds to about 3,500 kilocalories, so a daily deficit of 500 would mean about a pound a week. This is a simplification: the body adapts, water weight fluctuates, and energy expenditure changes as weight changes, so real progress usually slows. Moderate adjustments of 10% to 20% from maintenance are easier to sustain than extreme ones, and anyone with a medical condition should get professional guidance before dieting.

Macronutrients provide different energy per gram: protein and carbohydrate about 4 kcal per gram, fat about 9 kcal per gram (alcohol about 7). To convert a calorie target and a percentage split into grams, multiply the target by the percentage and divide by the kcal per gram.

Example: a 2,000 kcal target with a 30% protein, 40% carbohydrate, 30% fat split.

• Protein: 2,000 × 0.30 ÷ 4 = 150 g
• Carbohydrate: 2,000 × 0.40 ÷ 4 = 200 g
• Fat: 2,000 × 0.30 ÷ 9 ≈ 66.7 g

Check: 150 × 4 + 200 × 4 + 66.7 × 9 = 600 + 800 + 600 = 2,000 kcal.

Instead of a percentage, many people set protein per kilogram of body weight. Dietary reference values for general adults are around 0.8 g per kg; guidance for people who train regularly is often cited in the range of roughly 1.2 to 2.0 g per kg, depending on goals. For a 65 kg person, 1.6 g per kg is 104 g, or 416 kcal. Higher intakes may not suit people with kidney disease or other conditions, so check with a clinician.

• Treat the number as a hypothesis. Track intake and weight for two to four weeks, then adjust by about 100 to 200 kcal.
• Use the same scale, time of day and measurement habits to reduce noise.
• Compare trends in weekly averages, not single days.
• Remember that food labels and portion estimates are themselves approximate.
• Do not set calories below levels recommended by a health professional.

Calculators are not designed for children, pregnant or breastfeeding people, people with eating disorders or chronic disease, or elite athletes. For those groups, advice from a qualified clinician or dietitian is more appropriate than a general formula.

• Choosing an activity level that is too high.
• Mixing pounds and kilograms, or inches and centimetres.
• Treating the output as exact.
• Setting an aggressive deficit without medical advice.
• Forgetting that macros must add up to the calorie target.

The BMR and TDEE calculators implement the formulas above. The Macro Calculator converts a calorie target into grams, and the Protein Need tool works from body weight. Educational estimates only.