Calorie deficit calculator: how to find your real number

A calorie deficit is the gap between the energy your body burns and the energy you eat. Eat 400 kcal less than you burn, and over a week you've created roughly a 2,800 kcal gap — about 0.3–0.4 kg of fat. That's the entire mechanism. Every weight-loss program in existence is some flavour of this.

Calculating your deficit takes 30 seconds. Below is how to do it without falling for the three traps that make most online calculators worse than guessing.

Step 1. Estimate your TDEE

Your TDEE — total daily energy expenditure — is what you burn in 24 hours, all-in: basal metabolism, digestion, fidgeting, walking, training. Use the Mifflin-St Jeor formula for the resting part, then multiply by an activity factor:

• Sedentary (desk job, no gym): TDEE ≈ BMR × 1.2
• Light (walking + 1–2 light sessions/wk): BMR × 1.375
• Moderate (3–5 sessions/wk): BMR × 1.55
• Active (6+ sessions/wk, physical job): BMR × 1.725

Don't sweat the precision — the activity multipliers are rough. Pick the one that matches your honest week, not your aspirational one. Our BMR vs TDEE guide walks through the formula in detail.

Step 2. Subtract a small number

For most people, a 300–500 kcal/day deficit is the right size. That's where you lose mostly fat, keep most of your muscle, and don't feel hollowed out. Aggressive cuts (700+ kcal/day) work briefly, then crash. The body lowers thermogenesis, hunger spikes, sleep gets worse — adherence falls apart by week three.

If your TDEE is 2,400, your deficit calorie target is 1,900–2,100. That's it. Don't optimise further until you've held it for four weeks.

Step 3. Set your macros inside the deficit

Inside that calorie target, prioritise protein first. Aim for 1.6–2.2 g per kg of bodyweight (see our protein per kg piece). Fat: don't go below 0.7 g/kg — hormones suffer. Carbs fill the rest. A 70 kg person on 2,000 kcal might run 140 g protein / 65 g fat / 220 g carbs. The numbers will adjust as you lift more or less.

The three traps in online calculators

First, false precision. "Your TDEE is 2,427.6 kcal" is theatre. Real day-to-day variance is ±200 kcal from sleep, training, stress, and water. Treat any TDEE estimate as a starting bet.

Second, ignoring weight change feedback. Your TDEE estimate is wrong until proven right. After two weeks, look at your weekly average weight — if it dropped ~0.4 kg/week, the deficit is right. If it didn't move, your real TDEE is lower than the formula said. Adjust by 100 kcal and check again in another 14 days.

Third, calculating once and never updating. As you lose weight, your TDEE drops. A 90 kg person who reaches 80 kg burns ~150 kcal less per day at rest. Re-run the math every 5 kg of loss.

How KusWise handles this

Use our free calculator to get your TDEE and macro split — no sign-up. Then open KusWise in Telegram (send /start) and the bot will track your daily calories against that target, flag weekly drift, and quietly suggest a 100-kcal adjustment if your trend stalls. The math is right because the inputs are real meals, not aspirational ones.

"Don't overthink the calculator. Pick a number, run it for two weeks, then let your weight tell you if the bet was right."