Calorie deficit calculator
Your real daily expenditure, how many calories to eat to lose fat, and at what pace — using the Mifflin-St Jeor formula, the same one behind our macro calculator.
Fill in your details and your target calories appear here instantly — no sign-up.
What a calorie deficit is (and is not)
A calorie deficit means eating fewer calories than your body burns in a day. It is the one non-negotiable condition for fat loss: without a deficit there is no loss, on any diet and any meal schedule. Everything else — fasting, keto, skipping evening carbs — is a different road to the same place.
The trap is in the size. An oversized deficit works for two weeks and then collects its price: more hunger, worse training, muscle loss and rebound. That is why this calculator works with percentages of your expenditure (−12%, −20%, −27%) instead of subtracting a fixed number, and caps the result at 1,200/1,500 kcal.
The second common mistake is watching only calories. In a deficit, protein decides how much muscle you keep: the reference for people who train sits between 1.6 and 2.4 g per kilo of body weight. Once you have your target calories, split them with the macro calculator — it uses the same formula and picks up exactly where this one ends.
Frequently asked questions
How is a calorie deficit calculated?
First you estimate total daily energy expenditure (TDEE): basal metabolic rate with the Mifflin-St Jeor formula multiplied by your activity level. Then you subtract a percentage of that expenditure — usually between 10% and 25% — and that is your calorie target. This calculator does both instantly.
How many calories should I eat to lose fat?
Fewer than you burn, but not too few. For most people, 12% to 25% below daily expenditure: with a 2,500 kcal expenditure, between 1,875 and 2,200 kcal per day. Beyond 25%, hunger, muscle loss and rebound all increase.
Which deficit is best: gentle, standard or aggressive?
Standard (−20%) is the usual starting point: visible progress without dragging yourself through the day. Gentle (−12%) fits if you train hard and want to keep performance. Aggressive (−27%) only makes sense short-term with high protein. The best deficit is the one you can sustain for weeks, not days.
How much weight will I lose per week?
A kilogram of fat holds roughly 7,700 kcal, so a 500 kcal/day deficit loses about half a kilo per week. The scale fluctuates with water and glycogen: compare weekly averages, not single days.
Can I lose fat and gain muscle at the same time?
In some cases, yes — especially if you are new to strength training or coming back after a break. It takes a moderate deficit and high protein. That is body recomposition, and we have a full guide dedicated to it.
What if my result is very low, like 1,200 kcal?
The calculator caps the result at 1,200 kcal (women) or 1,500 kcal (men): sustained intakes below that are not safe without professional supervision. If your target lands there, a gentler deficit plus more daily movement beats cutting more food.