Calorie Deficit and TDEE: How to Calculate Your Daily Calories

TDEE and the deficit rule in one example

TDEE, or total daily energy expenditure, is the number of calories your body burns in an average day, including rest, digestion, work and exercise. You estimate it in two steps: first calculate your BMR, the energy you would spend lying still all day, then multiply it by an activity factor between 1.2 and 1.9. Eat about 500 kcal below the result and you lose roughly 0.5 kg per week; eat 500 kcal above it and you gain at the same pace.

Here is the method on a concrete case. A 30 year old male, 175 cm tall and 80 kg, gets a BMR of 10 × 80 + 6.25 × 175 - 5 × 30 + 5 = about 1,749 kcal. He works a desk job but trains three evenings a week, so he multiplies by 1.55 for a moderately active lifestyle: 1,749 × 1.55 = about 2,711 kcal per day. His weight loss target is therefore about 2,211 kcal per day, which should take off around half a kilogram every week without much hunger.

Everything else in this guide refines those two steps: the formula written out for men and women, the activity factor table, what counts as a safe deficit, and how protein and lifting keep the loss coming from fat.

Step 1: the BMR formula (Mifflin-St Jeor)

The Mifflin-St Jeor equation is the standard way to estimate BMR from four numbers you already know. For men: BMR = 10 × weight in kg + 6.25 × height in cm - 5 × age + 5. For women: BMR = 10 × weight in kg + 6.25 × height in cm - 5 × age - 161. The weight term dominates, which is why heavier bodies burn more even at complete rest, the age term explains why maintenance calories drift down slowly through adult life, and the 161 constant is the entire difference between the sexes.

Work the female formula once for scale: a 35 year old woman weighing 65 kg and standing 165 cm gets 10 × 65 + 6.25 × 165 - 5 × 35 - 161 = 650 + 1,031 - 175 - 161 = about 1,345 kcal at rest. Note that the equation is built on kilograms and centimetres; if you measure in pounds and inches, convert first (1 pound = 0.4536 kg, 1 inch = 2.54 cm). It is an estimate rather than a lab measurement, but it is accurate enough to build a real plan on for most healthy adults; children, pregnancy and very muscular builds need professional assessment.

Step 2: pick your activity factor honestly

The multiplier covers everything between lying still and an athletic life: everyday movement, job demands and deliberate exercise. The five standard bands are below. Choose the band that matches a typical week, not your best week; the gap between two neighbouring levels is worth roughly 150 to 250 kcal per day, which alone explains many disappointing results.

Two cautions keep the number honest. First, exercise calories are already inside the multiplier, so a moderately active person who also logs a spin class should not add those calories back on top. Second, when in doubt pick the lower band: the cost of underestimating is a slightly slower plan, while overestimating quietly erases the deficit you thought you had.

A useful reality check: if your weight has been stable for months, your true TDEE equals what you have been eating, and the calculation should roughly agree. When the two disagree by more than 10 percent, trust the scale history and adjust the activity factor rather than blaming the formula.

Step 3: choose a safe deficit

A deficit of 500 kcal per day is the default because it maps to about 0.5 kg (one pound) of body fat per week for many adults, and it is small enough to sustain for months. Percentages work too: cutting 15 to 20 percent of TDEE gives a similar pace and scales naturally for smaller or larger bodies. A 2,711 kcal maintenance therefore suggests roughly 2,200 to 2,300 kcal for steady loss.

Floors matter more than ceilings. Most guidance warns against eating below about 1,200 kcal for women or 1,500 kcal for men for any length of time without medical supervision, because very low intakes make adequate protein, fibre and micronutrients nearly impossible and accelerate muscle loss. Losing faster than about 1 percent of body weight per week starts costing muscle, not just fat.

There is also a lifestyle floor: if the plan makes training miserable, wrecks sleep or demands a social life you refuse to give up, it will not survive contact with reality. Pick an intake you can imagine holding for six months, then let the pace be whatever that intake produces.

Protein and lifting: keeping the muscle you have

In a deficit your body hunts for extra energy, and without protection it takes some from muscle. Protein is the main defence: roughly 1.6 to 2.2 g per kg of body weight per day is the range most evidence supports for people dieting and training. For the 80 kg example that is about 130 to 175 g of protein spread across the day. Protein also carries the highest thermic effect of the three macros and blunts hunger, which quietly makes the deficit easier to hold.

Resistance training is the other half of the protection. Lifting two to four times a week signals that the muscle is still needed, so more of the loss comes from fat; beginners get a bonus, since building new muscle while dieting is still possible in the first year of training. Sleep and stress complete the picture: short sleep shifts weight loss away from fat and toward lean tissue, and it raises the appetite hormones that make a deficit feel unbearable. Keep cardio moderate, keep lifting heavy, and short diet breaks at maintenance can help during long cuts.

The example continued: what eight weeks looks like

Continue the 30 year old male from the top: 2,711 kcal maintenance, eating about 2,200 kcal per day, a 500 kcal daily deficit. Over a week that is a 3,500 kcal shortfall, close to the energy stored in half a kilogram of body fat, so the plan projects about 0.5 kg lost per week and roughly 4 kg across eight weeks. Real scales rarely follow projections that neatly, and that gap is not failure but normal measurement noise. A kitchen scale for food and a simple weekly average of weigh ins beat any gadget sold for the purpose.

Water, sodium, carbohydrate intake and menstrual timing move scale weight by a kilogram or more in either direction within days, so judge progress on a 2 to 3 week rolling average of morning weigh ins. Expect TDEE to fall as you get lighter: at 76 kg the BMR of the same man drops by about 40 kcal, and a smaller body also burns less in motion, so recalculate after every 4 to 5 kg of change. A two week plateau with honest tracking calls for a small adjustment, not a crash diet.

Calorie deficit myths worth dropping

A few stubborn ideas survive because each holds a grain of truth stretched out of shape. Sorting them now saves months of misdirected effort, because most stalled diets fail on tracking or adherence, not on one of these mysteries.

If a claim promises results without sustained energy balance, someone is selling something. The arithmetic above is boring, but it is the mechanism every working diet uses, from keto to intermittent fasting to plain portion control.

• Myth: certain foods burn fat. No food creates a deficit; the difference between salad and cookies is how easily each leads to overeating.
• Myth: eating after 8 pm stops weight loss. Total daily intake decides; late snacks usually just add calories.
• Myth: small frequent meals stoke the metabolism. Meal frequency barely changes energy expenditure; the weekly total matters.
• Myth: a deficit permanently wrecks your metabolism. TDEE does fall with body size and adaptation, but it is nowhere near the total shutdown some diets blame.
• Myth: you must cut an entire food group. Removing a group works only when it lowers total intake; balance keeps the diet livable.