Calorie Deficit Calculator

A calorie deficit is the gap between the energy you take in as food and the energy your body uses over the same period. When you consistently eat fewer calories than you burn, your body does not have enough fuel to hold everything it has stored, so it draws on that reserve and body weight tends to fall.

Three energy balances worth separating

Maintenance calories are the intake that would keep your weight broadly steady at your current activity level. They are the baseline every other figure on this page sits on top of.

A calorie deficit is maintenance calories minus the extra energy you deliberately give up each day. Eating below maintenance is the mechanism behind most gradual weight loss.

A calorie surplus is the opposite: eating more than you burn. Surpluses are the usual mechanism behind weight gain, and they are sometimes used deliberately in structured weight-gain plans.

Weight change is not a switch you flip. It reflects whatever balance you hold across days and weeks, and a single day's eating rarely moves the scale in a predictable way.

A deficit is a running total

The arithmetic works the same way. Seven days at 300 kcal under maintenance is 2,100 kcal, which is roughly 0.25 kg of fat under the 7,700 approximation. The reverse is equally true: a single high-calorie day does not undo a fortnight of careful eating, and a single quiet day does not undo two weeks of consistency.

This is also why an occasional high day matters far less than it feels like it should. What changes the result is the average you settle on, not the worst individual day.

The calculation runs in four steps, each one feeding the next. The order matters, because the deficit is only meaningful once you know what you would otherwise be eating to hold your weight steady.

Step 1 · Estimate BMR

Basal metabolic rate is an estimate of the energy your body needs at complete rest — breathing, circulation, and basic cell function. It is calculated from your sex, age, height, and weight using the Mifflin-St Jeor equation.

Men: 10 × kg + 6.25 × cm − 5 × age + 5

Women: 10 × kg + 6.25 × cm − 5 × age − 161

Step 2 · Apply an activity multiplier to reach TDEE

TDEE, or total daily energy expenditure, is what you actually spend across a whole day. Resting energy is only part of it, so BMR is multiplied by a factor reflecting how active you are.

TDEE = BMR × activity multiplier

The result is your estimated maintenance calories.

Step 3 · Convert your goal into a daily deficit

Your chosen weekly weight-loss goal is converted into the number of calories to shave each day, using the energy content of body fat as the conversion factor.

Daily deficit = (weekly goal in kg × 7,700) ÷ 7

Step 4 · Subtract the deficit from maintenance

What remains is the daily calorie target: the estimated intake that would put you in the deficit you asked for.

Daily target = maintenance calories − daily deficit

Step 5 · Normalise your units

Height and weight can be entered in metric or imperial, and the weekly goal is always held in kilograms. Imperial entries are converted before any of the maths runs, so 5′ 10″ and 176 lb give the same result as 177.8 cm and 80 kg. Only the inputs you can type in change; the calculation always works in one consistent set of units.

177.8 cm = 5′ 10″ · 80 kg = 176 lb

Turn a weekly goal into a daily number

Start with the rate you want to lose each week, then divide the weekly energy cost across seven days:

Daily deficit ≈ (weekly weight-loss target in kg × 7,700) ÷ 7

A goal of 0.5 kg per week works out to roughly 550 kcal a day. A goal of 0.25 kg per week works out to roughly 275 kcal a day.

Subtract that from your maintenance calories

Once you know what you would eat to hold steady, the deficit tells you how much to give up. Subtracting one from the other gives the target:

Daily target = TDEE − daily deficit

If your maintenance calories are 2,700 and your chosen goal works out to a 550 kcal daily deficit, your target is 2,150 kcal a day.

What the 7,700 figure actually means

The 7,700 kcal-per-kilogram figure is a widely used approximation of the energy stored in a kilogram of body fat. It exists to convert a rate of weight change into a rate of energy change, and it is a planning estimate rather than a physical constant.

It is not a promise that a 7,700 kcal deficit will always produce exactly one kilogram of body-weight change, and it does not account for the difference between losing fat and losing a mix of fat, water, and other tissue. Treat the output as a sensible starting point and adjust it against what actually happens to you.

The same caution applies to the whole calculation. BMR and TDEE come from predictive equations, and predictive equations describe populations well enough to be useful without describing any one individual exactly.

There is no single deficit that suits everyone, and anyone promising you one number is oversimplifying. What is appropriate depends on your current maintenance calories, body size, activity level, goal, and circumstances — including how long you intend to sustain it and how you respond to lower intake.

A useful way to think about it is as a proportion of maintenance calories rather than a fixed number of calories. The same 500 kcal means something quite different to someone maintaining 1,800 kcal than to someone maintaining 3,000.

A larger deficit is not automatically better

Bigger deficits usually mean faster short-term change, but they also tend to be harder to sustain, harder to hit accurately, and harder to keep performing in. Many people find a moderate deficit that they can hold for months produces a better overall outcome than an aggressive one they abandon in weeks.

Very large deficits also narrow the gap between your target and the minimum intake a general calculator should hand back. Where a goal is very aggressive, the calculator reports an error on the weekly goal rather than showing you a number it would rather not recommend.

About the safety floor

This tool will not return a daily calorie target below 1,200 calories. That floor is a conservative guardrail built into the calculator, not a medical rule that applies to every person in every situation. Its purpose is to stop the tool presenting an extremely low target as an ordinary recommendation, and to flag a goal that is aggressive for the maintenance calories being used.

If your target falls below the floor, the calculator says so and leaves the choice with you — typically by suggesting a slower rate or a check on your activity level.

A calorie deficit is the mechanism behind most weight loss. When the energy you take in stays below the energy you spend across enough days and weeks, body weight generally trends downward. The arithmetic is straightforward; the biology is not instant, and the scale is a noisy instrument for reading it.

Daily deficit and weekly deficit

The daily deficit is the practical number, because that is what you adjust at each meal. The weekly figure is the same thing multiplied by seven, and it connects back to your goal in kilograms per week.

A 300 kcal daily deficit is 2,100 kcal a week, which maps to roughly 0.25 kg per week under the 7,700 approximation.

Expected rate versus actual scale readings

Calculated rates are long-run averages. Your scale measures something that moves around far more than that from day to day, for reasons that have little to do with fat.

Carbohydrate intake changes how much water your body holds, as does salt, caffeine, alcohol, a new training routine, stress, poor sleep, constipation, and the time of day you weigh yourself. A salty meal or a hard training day can mask a real deficit for several days, and the scale can swing a kilogram or more with no change in body fat.

That is why weekly averages are more informative than single readings, and why a two-week window tells you more than a two-day one. A calculated 0.5 kg per week can appear as one smooth half-kilo drop or as a jagged line trending downward over a month.

A deficit can come from either side of the balance: eat less, burn more, or a bit of both. Most people find it easier to move the food side than the activity side, because eating is something that happens several times a day while training fits around everything else.

Reduce intake without cutting out food groups

The most sustainable reductions are usually small, repeated adjustments rather than a sudden overhaul: trimming portion sizes, swapping a high-calorie snack for a piece of fruit, or leaving a little of a rich sauce on the plate. Removing whole food groups tends to be hard to sustain and easy to rebound from.

Choose foods that fill you up

Protein, fibre, and volume all help with fullness, which is what makes a lower intake bearable. This is the same reason the protein calculator on this site recommends a gram target per kilogram of body weight — protein is a useful anchor for meals when you are eating less overall.

Calorie deficit meals do not have to be a separate category of food. Ordinary meals built around protein and vegetables tend to work naturally, and they are easier to stick to than a special diet.

Increase activity

More daily movement raises total daily energy expenditure, which lowers the target you need to hit. Walking, standing more, cycling, or a couple of extra sessions a week all count — and because the calculator asks about your activity level, an honest answer here reduces how much you have to cut from food.

Track consistently rather than perfectly

The value of tracking is that it shows you where your estimate and reality differ. You do not need to weigh every gram; noticing consistently what you tend to underestimate is usually enough to close the gap. A rough log that you keep is far more useful than a precise one you abandon in a fortnight.

Avoid overly aggressive restriction

Cutting intake very hard tends to cost you muscle and training quality alongside fat, and makes the plan harder to hold. If you find yourself fighting the plan constantly, or your training and energy are falling away, a smaller deficit that sticks is the better trade.

The number is whatever falls out of one subtraction, and the subtraction is the whole idea:

Target calories = TDEE − calorie deficit

Your TDEE is your estimated maintenance calories. The deficit is whatever you have decided to give up each day. What remains is the intake that would put you in that deficit.

Why the answer is different for everyone

Two people asking the same question can be told very different numbers, because their maintenance calories differ. Someone smaller, older, or less active expends less energy and therefore needs a smaller absolute target. Someone larger or more active needs a larger one. The deficit is the variable you choose; the target is a consequence of it and of who you are.

That is also why a generic target is risky in a way a generic formula is not. A formula applied to your own numbers gives you a number specific to you. A figure copied from an article does not.

An estimate, not a measurement

This tool estimates your energy needs using established equations — Mifflin-St Jeor for BMR and a standard activity multiplier for TDEE. Those are well-established methods, and they are as accurate as equation-based calculators can be, but no version can claim to be the most accurate or fully exact. Actual energy needs vary between individuals, and the activity multiplier is a single number standing in for a real week.

Treat the target as a starting hypothesis. The real test is whether your weight trend over several weeks matches what you intended; if it does not, adjust the input that is most likely wrong rather than assuming the arithmetic is broken.

TDEE is the number everything else depends on. A calorie deficit calculator that skipped it would have nothing to subtract from, and any deficit you chose would be a guess about your maintenance rather than a calculation from it. That is why this page asks for your age, sex, height, weight, and activity level before it will suggest a target.

The relationship is a simple chain, and each link depends on the one before it:

BMR → TDEE (maintenance) → deficit → target

An error anywhere along that chain carries through. If BMR is overstated, TDEE is overstated, the target is too high, and the real deficit ends up smaller than intended. This is the single most common reason a calculated target does not match results in practice.

TDEE is an estimate too

Total daily energy expenditure is a modelled figure, not a measurement. It comes from an equation applied to a handful of inputs and then scaled by an activity multiplier, which means it cannot know about your genetics, your hormone levels, your muscle mass, your digestive efficiency, or the specific way you move during a normal week.

If you want a closer read, the TDEE calculator on this site works through the same BMR and multiplier step on its own, and the calorie calculator shows the same maintenance figure as a calorie target. All three use one shared method, so the maintenance number here will match the one you see there for the same inputs.

How TDEE is actually measured

In a laboratory, total daily energy expenditure can be measured directly: indirect calorimetry tracks the oxygen you breathe out and the carbon dioxide you breathe in to work out how much fuel you are burning. That is expensive and impractical for everyday use, so calculators estimate it instead.

Wearables and heart-rate monitors offer a middle ground, but they infer calories from movement data and heart rate rather than measuring metabolism, and they carry their own error. Every approach — including the one used here — has uncertainty attached, which is why the honest framing is an estimate adjusted against real results rather than a precise measurement.

If the scale has not moved after a few weeks of a calculated deficit, that is a common and unremarkable outcome rather than a sign that something is wrong with you. Several ordinary things can account for it, and they are worth checking before you conclude the plan has failed.

Intake is usually underestimated

Restaurant meals, cooking oils, sauces, drinks, and snacks are the usual culprits, and the gap between a remembered day and a weighed day is often several hundred calories. Portion sizes also drift upward over time without being noticed.

Activity is usually overestimated

This is the more common error of the two. A multiplier chosen from the "very active" option may reflect a few good weeks rather than a normal one, and desk-bound days with a weekend workout often get labelled as moderately active. The calculator takes your word for the activity level, so an optimistic choice there quietly inflates the target.

Water can mask a real deficit

A carb-heavy meal, a salty meal, new training, or a stressful week can hold extra water for several days. If you happen to weigh during that window, the scale shows no progress even though the underlying balance has changed. The same effect in reverse explains the sudden drops that have nothing to do with fat loss.

Weight fluctuates and needs do too

Body weight moves around day to day quite normally. Maintenance needs also drift as you get more active, change your job, alter your sleep, or your body composition shifts. A target calculated months ago may no longer describe your current maintenance, and recalculating is often more useful than cutting harder.

The real deficit may simply be smaller

Put the pieces together and a small shortfall in each direction compounds: intake underestimated by a few hundred calories, activity slightly overstated, and a week of noisy water retention can together hide a genuine but modest deficit. Before treating this as a failure, check that you are comparing weekly averages rather than single readings, and re-run the calculation with your most honest activity level.

Yes — losing fat and gaining muscle at the same time does happen. It is a real outcome, particularly for people who are relatively new to resistance training, are returning after a break, or still have beginner-level muscle gains available to make.

It is also not something that can be promised. Recomposition is a possibility, not a plan that works on demand, and for many people the realistic expectation while eating in a deficit is to preserve muscle and lose fat. A large deficit is unlikely to be compatible with muscle gain, because the conditions that favour new muscle tissue need surplus energy and enough protein to build from.

What the outcome depends on

Training status. The closer you are to your potential, the less you have available to gain, and the more likely you are to lose a little muscle in a deeper deficit.

Protein intake. Adequate protein protects muscle while you are in a deficit, which is why a protein target per kilogram of body weight is worth setting alongside a calorie target.

Size of the deficit. A moderate deficit is far more compatible with training performance and muscle retention than an aggressive one.

Training and recovery. Progressive resistance work gives the signal to build muscle; sleep and recovery give it the conditions to happen.

Individual circumstances. Age, hormone status, training history, and health all affect what is realistic, and they are not visible to a calculator.

Keeping muscle while losing fat

Whether or not you gain muscle, protecting what you already have is usually the achievable goal in a deficit. Four things do most of that work.

Protein. Spread a daily protein target across meals rather than eating it in one sitting, so intake is steady while you are eating less overall.

Resistance training. Keep lifting, and keep progressing it. The stimulus to retain muscle is the training itself, not the calorie balance.

A moderate deficit. The deeper the cut, the more likely some muscle goes with the fat, and the more your training quality and recovery suffer.

Sleep. Fatigue and poor sleep make every other part of this harder, from appetite control to recovery between sessions.

Sex is one of the inputs used to estimate BMR, and therefore TDEE and your final calorie target. The Mifflin-St Jeor equation used here has separate constants for men and women, so choosing the option that matches you changes the maintenance figure the whole calculation rests on.

It changes the arithmetic, not the principle. The same relationship between maintenance calories, deficit, and target applies to everyone. There is no single deficit or calorie target that is correct for women as a group — the right figure still depends on your own size, age, activity, and goal, and it varies from person to person in exactly the way it does for anyone else.

Pregnancy and breastfeeding

This is a general-purpose calculator and is not intended to determine calorie restriction during pregnancy or breastfeeding. Energy needs in those circumstances change considerably and are not described by a Mifflin-St Jeor estimate with a standard activity multiplier.

If you are pregnant or breastfeeding, please do not apply a generic calorie-deficit target from a tool like this. Speak with a qualified healthcare professional or a registered dietitian, who can take your individual circumstances into account.

When to involve a professional

A general calculator assumes a healthy adult managing their own energy intake. That assumption stops holding in several situations, and it is worth knowing where the edges are.

If you are under 18, over 65, pregnant, or breastfeeding, or if you have a medical condition, a history of disordered eating, or take medication that affects appetite or metabolism, a generic estimate is the wrong tool. So is a deficit you would describe as extreme.

In those cases the useful question for a professional is not "what number is mine" but "what approach is appropriate for me" — they can weigh up factors a calculator has no way of seeing.