Calorie Deficit Calculator

Enter age, sex (used in the Mifflin-St Jeor equation), height, and weight in the units your form expects. Pick the activity level that best matches a typical week — not your best week of the year.

Select a goal: maintenance, fat loss, or muscle gain. Read the suggested calorie target alongside BMR and TDEE. Revisit the form after every 4–8 kg (10–15 lb) of weight change or a major shift in training, since both BMR and activity estimates drift.

BMR (kilocalories per day at rest) uses weight W in kg, height H in cm, and age A in years:

• Men: BMR = 10W + 6.25H − 5A + 5
• Women: BMR = 10W + 6.25H − 5A − 161

TDEE multiplies BMR by an activity factor (often roughly 1.2 sedentary through 1.9 for very active). Your app's exact multipliers may differ slightly by implementation. Goal calories then add or subtract a deficit/surplus from TDEE — commonly 250–500 kcal/day for moderate fat loss or lean gain.

TDEE stands for Total Daily Energy Expenditure — the total number of calories your body burns in a day. It includes your Basal Metabolic Rate (the energy needed just to keep your body functioning at rest), the thermic effect of food (energy used to digest meals), and physical activity (exercise plus everyday movement). Knowing your TDEE lets you set a calorie target that aligns with your goal, whether that's losing weight, gaining muscle, or simply maintaining your current body composition.

A calorie deficit occurs when you consume fewer calories than your body uses. Over time, your body draws on stored fat for the missing energy, resulting in weight loss. A deficit of about 500 calories per day is widely recommended because it produces steady loss (roughly 1 lb per week) without the metabolic slowdown and muscle loss associated with extreme restriction. Tracking your intake with a food diary or app and recalculating every 4–6 weeks helps keep your numbers accurate as your body changes.

Activity level is the biggest variable in the calculation. Sedentary means little to no exercise — desk jobs with minimal walking. Lightly active is 1–3 days of light exercise per week. Moderately active means 3–5 days of moderate exercise. Very active is hard exercise 6–7 days per week, and extremely active covers athletes or highly physical jobs. When in doubt, choose one level lower than you think — most people overestimate their activity, which can mask a deficit and stall progress.

Equations estimate averages for people similar to you on paper — they cannot see your genetics, thyroid status, sleep debt, or fidgeting (NEAT). Treat the output as a starting budget. Track weight trend for 2–3 weeks; if it does not move as expected, adjust intake by 100–200 kcal and reassess rather than chasing perfection on the first guess.

Protein helps preserve lean mass while eating less. Common targets land near 0.7–1.0 g per lb body weight (1.6–2.2 g/kg) for lifters in a deficit, with flexibility for preference and kidney guidance from your clinician. Calories still matter for weight change; protein matters for what fraction of that change is muscle vs fat.

Water retention from sodium, hormones, new exercise soreness, and carb refeeds can hide fat loss on the scale for days or weeks. Logging errors (oils, sauces, weekends) also add up. If the trend is flat for a month, re-check TDEE inputs and measured intake before slashing calories further.

• Desk job + new gym habit: Bump activity from sedentary to light or moderate when you actually train 3×/week — then hold steady for a month to validate the estimate.
• Postpartum: Use clinician guidance for intake; generic calculators do not replace medical nutrition advice during lactation or recovery.
• Bulk season:A small surplus (200–300 kcal over TDEE) often limits fat gain better than aggressive "dirty" bulks while still supporting strength progress.