Calorie & TDEE Calculator

How to Use the TDEE Calculator

1. 1Enter your age, sex, height, and weight in metric or imperial units.
2. 2Pick your activity level, which multiplies BMR into TDEE. Add body fat % to unlock the more accurate Katch-McArdle formula.
3. 3Choose a goal — lose, maintain, or gain — to apply a calorie deficit or surplus.
4. 4Read your goal calories, macro breakdown, and per-meal targets.

Worked Example: From BMR to a Daily Calorie Target

Take a 30-year-old man, 180 cm tall and 80 kg. The Mifflin-St Jeor formula for men is BMR = 10 × weight + 6.25 × height − 5 × age + 5 = 10 × 80 + 6.25 × 180 − 5 × 30 + 5 = 800 + 1125 − 150 + 5 = 1,780 kcal. That is what his body would burn lying in bed all day. Applying a “moderately active” multiplier of 1.55 gives TDEE = 1,780 × 1.55 ≈ 2,760 kcal — his true maintenance level.

To lose about one pound of fat a week he subtracts the standard 500 kcal/day deficit, landing at a target of roughly 2,260 kcal. The macro split then divides that total: on a high-protein 40/30/30 plan, protein is 40% × 2,260 ÷ 4 ≈ 226 g, carbs 30% × 2,260 ÷ 4 ≈ 170 g, and fat 30% × 2,260 ÷ 9 ≈ 75 g. Treat these as a starting point, not gospel — activity multipliers are population averages, and individual NEAT can swing TDEE by 300–500 kcal. Track your weight for two weeks and adjust by 100–150 kcal if the scale isn't moving as predicted.

The Four BMR Formulas — and Which One to Use

Everything starts with Basal Metabolic Rate, the calories your body burns at complete rest, and there is more than one way to estimate it. Mifflin-St Jeor is the modern default and the most validated equation for the general population; it uses age, sex, height, and weight, and is what the calculator uses when you do not enter a body-fat percentage. Harris-Benedict is the classic 1919 formula (later revised); it tends to run a little high and is included mainly for comparison. The other two work differently: both Katch-McArdle and Cunningham calculate BMR from lean body mass rather than total weight, which requires a body-fat percentage but is more accurate for lean, muscular, or athletic bodies. The reason they are better in those cases is that muscle, organs, and bone drive almost all of your resting burn while fat tissue is nearly inert — so a formula that models lean mass directly sidesteps the population averages baked into the weight-only equations. If you know your body fat, enter it and prefer Katch-McArdle; if you do not, Mifflin-St Jeor is the reliable choice.

Activity Multipliers and Why TDEE Is Really a Range

BMR is only the resting baseline. To reach TDEE — the total you actually burn — the calculator multiplies BMR by an activity factor, from roughly 1.2 for sedentary up to around 1.9 for extremely active. That single multiplier is the biggest source of error in any TDEE estimate, because it is a population average papering over enormous individual variation. The main culprit is NEAT (non-exercise activity thermogenesis): the calories you burn fidgeting, standing, walking to the shop, and generally moving through the day. Two people with the same stated activity level can differ by 300–500 kcal a day in NEAT alone. This is why you should treat your calculated TDEE as an informed starting hypothesisrather than a precise figure — the real number is revealed only by eating consistently for a couple of weeks and watching what the scale actually does.

Deficit, Surplus, and a Realistic Rate of Change

Body composition follows energy balance. Eat below your TDEE and you are in a deficitand lose fat; eat above it and you are in a surplus and gain weight; eat at it and you maintain. A pound of body fat stores roughly 3,500 kcal, which is where the standard 500 kcal/day deficit for about a pound of loss per week comes from. Larger deficits of 750–1,000 kcal can work for short, well-planned phases but raise the risk of muscle loss and low energy, which is why the calculator enforces a sensible floor. For gaining, a modest surplus of 250–500 kcal builds muscle with less fat than an aggressive bulk. The guiding principle is patience: slower, sustainable changes preserve muscle, are easier to adhere to, and are far more likely to stick than crash approaches that trigger rebound.

Making Sense of Your Macros

Total calories decide whether you gain or lose; macronutrients shape the quality of that change. Once your goal calories are set, they are divided among protein (4 kcal per gram), carbohydrate (4 kcal/g), and fat (9 kcal/g). Protein is the macro to anchor first: adequate protein preserves muscle in a deficit and supplies the raw material for growth in a surplus, and it is the most satiating and thermically expensive to digest. Carbohydrate fuels training and higher-intensity work, while dietary fat supports hormones and the absorption of fat-soluble vitamins, so neither should be cut to zero. The preset ratios — high protein, low carb, keto, high carb — simply shift the balance of carbs and fat to suit your training style and preferences while keeping protein high; there is no single “best” split, only the one you can hit consistently.

Metabolic Adaptation and Diet Breaks

One reason a fixed calorie number stops working is metabolic adaptation: as you lose weight, a smaller body burns fewer calories, and prolonged dieting can nudge NEAT and hormones downward too, so your TDEE drifts below the original estimate. This is normal, not a metabolism that is “broken.” The practical response is to recalculate periodically as your weight changes and to adjust intake by 100–150 kcal when progress stalls for a couple of weeks. Structured diet breaks — a week or two eating at maintenance after a long deficit — can ease the psychological load and partially reset the downward drift before you resume. The overarching lesson is that these numbers are a dynamic starting point to be steered with real feedback, not a one-time calculation to obey indefinitely.