Calorie Deficit Calculator

What Is a Calorie Deficit?

A calorie deficit exists whenever your daily energy intake is lower than your daily energy expenditure. It is a state, not a food or a plan: you can be in one eating pasta and out of one eating salad. Nothing else on this page matters if that gap is not open.

The deficit is the mechanism every diet shares

Cutting carbohydrate, eating in an eight-hour window, replacing breakfast with a shake, filling half the plate with vegetables — each of these is a tactic for eating fewer calories than you burn without having to think about calories directly. They work when they produce a deficit and stop working when they do not, which is why the same person can lose weight on two contradictory diets and regain it on both.

That makes the arithmetic here the honest core of the whole business. What a calorie deficit calculator adds is scale: instead of hoping a rule of thumb produces a gap, you set the size of the gap deliberately and get the intake figure that opens it.

The deficit and your daily target are two different numbers

People use "calorie deficit" to mean both the size of the gap and the number of calories to eat, and the confusion costs real progress. The gap is the smaller number. Your eating target is maintenance minus the gap.

Enter 2,500 maintenance and choose 1 lb a week and the calculator reports both: a 500-calorie deficit and a 2,000-calorie target, with 3,500 calories as the shortfall across the week. If someone tells you they are "eating a 500-calorie deficit", they mean 500 below their own maintenance — which is 2,000 a day for that person and 1,350 a day for someone whose maintenance is 1,850.

What the units mean

Everything here is in kilocalories per day, written kcal on packaging and spoken as calories in ordinary English. One kilocalorie is 4.184 kilojoules, so a 2,000 kcal target is 8,368 kJ if your food labels use the metric unit. The weekly figure the calculator prints is simply the daily deficit multiplied by seven.

For scale, the NHS gives 2,500 kcal a day as an average man's requirement and 2,000 kcal for an average woman. Those are population averages, not personal maintenance — which is exactly why this tool asks you for your own number rather than assuming one.

How Do You Calculate a Calorie Deficit?

Two multiplications and one subtraction. The calculator does no estimating of its own: it takes the maintenance figure you supply, converts your chosen rate into calories, and subtracts.

The formula, written out

The 500 comes from the convention that a pound of body tissue is worth about 3,500 calories, a figure published by Wishnofsky in 1958. Spread across seven days, 3,500 divided by 7 is 500 — which is the entire origin of the advice to "cut 500 calories a day". A kilogram works out at roughly 7,700 calories on the same convention.

Daily deficit (kcal) = target rate (lb per week) × 500

Daily target (kcal) = maintenance (TDEE) − daily deficit

Weekly shortfall (kcal) = daily deficit × 7

The rate options translate directly: 0.5 lb/week is a 250-calorie daily deficit, 1 lb/week is 500, 1.5 lb/week is 750 and 2 lb/week is 1,000. The calculator also prints the metric equivalent of the rate you chose — 0.23, 0.45, 0.68 and 0.91 kg per week respectively.

Step by step

• Get your maintenance calories. This is your total daily energy expenditure — resting metabolism plus digestion, daily movement and training. It is the one number the calculator cannot work out for you.
• Enter it in the maintenance field. Values below 1,200 or above 6,000 are rejected with a prompt rather than calculated.
• Choose a target rate: 0.5, 1, 1.5 or 2 pounds a week.
• Multiply that rate by 500 to get the daily deficit.
• Subtract the deficit from maintenance. That is your daily calorie target, the large number the calculator returns.
• Multiply the deficit by 7 for the weekly shortfall, and read the flags: a note under 1,500 kcal, a warning under 1,200.

Worked example: 2,500 maintenance at 1 pound a week

The standard case, and the one behind most of the advice you have read.

Daily deficit = 1 × 500 = 500 kcal
Daily target  = 2,500 − 500 = 2,000 kcal
Weekly        = 500 × 7 = 3,500 kcal below maintenance

Result returned by this calculator

2,000 kcal/day

No flags: 2,000 is comfortably clear of both thresholds. The same maintenance at the gentle rate returns 2,250, at the aggressive rate 1,750, and at the steep rate exactly 1,500 — the last value that escapes a note by a single calorie.

Worked example: 1,850 maintenance at 1.5 pounds a week

A smaller person asking for a fast rate, which is where the flags start doing work.

Daily deficit = 1.5 × 500 = 750 kcal
Daily target  = 1,850 − 750 = 1,100 kcal
Weekly        = 750 × 7 = 5,250 kcal below maintenance

Result returned by this calculator

1,100 kcal/day ⚠

The tool returns the number and warns that it sits below 1,200 kcal — too aggressive to run without medical supervision. The same 1,850 maintenance returns 1,600 at the gentle rate with no flag, 1,350 at the standard rate with a note, and 850 at the steep rate with the same warning. Identical instructions produce very different levels of aggression depending on whose maintenance they are subtracted from.

Where the maintenance number comes from

Everything downstream inherits the accuracy of this one input. If your maintenance estimate is 300 calories high, so is your target, and the deficit you think you are running is 300 calories smaller than you believe — enough to erase the gentle rate outright.

The accepted range of 1,200 to 6,000 is deliberately wide: it covers a small, sedentary adult at one end and a heavy manual worker or endurance athlete at the other. Anything outside it returns the prompt "Enter your maintenance calories (TDEE), 1,200–6,000" instead of a target, because a figure that far out is almost always a typo.

If you do not have a maintenance figure yet, produce one first with the TDEE Calculator.

Calorie Deficit Chart: Targets by Maintenance

Every figure in this chart came out of this calculator. Find the row nearest your maintenance and read across; (note) marks a target under 1,500 kcal and (⚠) marks one under 1,200, exactly as the tool flags them.

Where the flags switch on

The thresholds are sharp rather than fuzzy, and it is worth knowing exactly where they fall so a flag does not read as arbitrary. At 1 lb a week, maintenance of 2,000 returns 1,500 with no note; 1,999 returns 1,499 and picks one up. Maintenance of 1,700 returns 1,200 with a note, while 1,699 returns 1,199 and triggers the warning.

At the steep rate the same boundaries arrive 1,000 calories higher up the scale: 2,500 maintenance returns a clean 1,500, 2,499 returns 1,499 with a note, and anything under 2,200 returns a warning. Read the other way round, that tells you the entry price of each option — the 2 lb/week rate only produces an unflagged target if your maintenance is 2,500 or above.

The same deficit is not the same demand

The calculator subtracts a flat number of calories, so the severity of a given rate depends entirely on how big your maintenance is. Here is each option as a percentage of the maintenance it is taken from:

The standard rate is a fifth of the day's energy for someone at 2,500 and nearly a third for someone at 1,600. When a friend's calorie target seems absurdly generous or punishing next to yours, this table is usually the whole explanation.

What the arithmetic projects over time

These are extrapolations of the same rule, not predictions the calculator makes for you. They are the ceiling of what the arithmetic allows, and the section below explains why real loss comes in under it after the first month or two.

The gentle rate looks negligible in the four-week column and respectable in the six-month one. That is the trade the whole page turns on: 13 pounds you barely noticed losing against 52 pounds you almost certainly could not have held the intake for.

How to Read Your Result

The calculator returns one headline number and three supporting lines, and each says something different about the plan you have just described.

The four lines it gives you

Nothing in the output depends on your body weight, sex, age or body composition, because the calculator is not given them. It is doing subtraction on the maintenance figure you supplied, and every judgment about whether the result suits you has to come from you or from the guidance below.

• The large figure is your daily calorie target — what to eat, not what to cut. For 2,500 maintenance at the standard rate it reads 2,000 kcal/day.
• The first line under it restates the arithmetic: maintenance, minus the deficit, giving the rate in pounds with the kilogram equivalent in brackets. This is where you check you selected the rate you meant to.
• The second line is the weekly shortfall — the deficit multiplied by seven, with a reminder that it rests on the 3,500-calories-per-pound convention. Any flag is appended here.
• The last line is the caveat the tool always prints: real loss will not be perfectly linear, because water shifts and metabolic adaptation bend the curve.

The note under 1,500 calories

Between 1,200 and 1,500 kcal the calculator prints a note rather than a warning: targets in that band are hard to sustain and hard to nourish adequately. The problem is not the energy so much as everything that travels with it. Protein, fiber, calcium, iron and the fat needed to absorb vitamins A, D, E and K all have to fit inside a shrinking budget, and the room for error disappears.

It is a nudge, not a prohibition. If the note appears at the rate you wanted, dropping one step usually clears it: maintenance of 1,850 returns 1,350 with a note at the standard rate and a clean 1,600 at the gentle one, at the cost of half a pound a week on paper.

The warning under 1,200 calories

Below 1,200 kcal the tool stops hedging and tells you the target is too aggressive to run without medical supervision. That floor is not arbitrary. The 2013 obesity guideline from the American College of Cardiology, the American Heart Association and The Obesity Society — and the NHLBI evidence review behind it — describe achieving a 500 to 750 kcal per day deficit, and state that a total daily intake of 1,200 to 1,500 kcal for women and 1,500 to 1,800 kcal for men will usually produce it. In other words, 1,200 is the bottom of the range clinicians prescribe with support in place, not a target to arrive at by arithmetic and pursue alone.

Very-low-calorie dieting also carries specific costs. NIDDK notes that losing weight very quickly raises the chance of forming gallstones, that crash diets are worth avoiding for that reason, and that for people with overweight or obesity the recommended starting point is a loss of 5 to 10 percent of body weight over about six months.

What to do when your target is flagged

A flag means the plan and the person do not fit together yet. Three of the four possible fixes are sensible:

• Slow the rate down. The cheapest fix, and the one the flag is suggesting. Every step down returns 250 calories a day to the target.
• Raise the other side of the equation. Maintenance is not fixed — adding daily walking or training lifts your TDEE, which lifts the target for the same rate of loss. This is the only route that makes a fast rate liveable for a small person.
• Accept a longer timeline at a rate you can eat at. Thirteen pounds in six months at an unflagged intake beats a flagged plan abandoned in week three.
• Do not simply re-enter a larger maintenance figure. Inventing 400 calories of TDEE to clear the flag changes the number on the screen and nothing about your body.

To see what specific activity is actually worth in calories before you count on it, run the sessions through the Calories Burned Calculator.

Choosing Your Rate: 0.5 to 2 Pounds a Week

The rate selector is the only judgment the calculator asks you to make, and it is the one people get wrong in a predictable direction. Here is what the published guidance actually supports.

What the guidelines say

The NHS advice is explicit and easy to hold against the four options here: aim to lose 1 to 2 lbs, or 0.5 to 1 kg, a week. That maps onto the standard and steep settings — with the caveat that the steep setting only produces an unflagged target above 2,500 maintenance.

The 2013 AHA/ACC/TOS guideline works in calories rather than pounds and prescribes a 500 to 750 kcal per day deficit, which is precisely the standard and aggressive options on this page. NIDDK frames the goal differently again, as 5 to 10 percent of starting body weight over six months: for a 200-pound person that is 10 to 20 pounds in 26 weeks — a range the gentle rate lands inside at 13 pounds, and the standard rate covers in 20 weeks or fewer.

Rate as a percentage of your body weight

A flat rate in pounds ignores how much body there is to take it from. The convention among people trying to lose fat while keeping muscle — set out in Helms and colleagues' 2014 review of natural bodybuilding preparation — is to lose roughly 0.5 to 1 percent of body weight per week. Translated into this calculator's four options:

For a sense of where the weight you are heading toward actually sits, compare your goal against the Ideal Weight Calculator.

That review studied lean trained athletes, so read the band as a guide to protecting muscle rather than a medical limit. The pattern it captures is sound and the calculator cannot apply it for you: the steep option is a reasonable ask at 250 pounds and an unreasonable one at 130.

The case for taking the slower option

The gentle rate is chosen far less often than it deserves, because 250 calories a day sounds like it cannot matter. Over 26 weeks the same arithmetic makes it 13 pounds — and it is 13 pounds taken at an intake most people can actually eat, which is the variable that decides whether month four happens at all.

There is also a quality argument. A larger deficit does not preferentially remove fat; it removes more of everything, muscle included, and the muscle you keep is what holds your maintenance calories up afterwards. Rapid loss also raises the gallstone risk NIDDK flags. If the choice is between the aggressive rate you abandon in five weeks and the gentle rate you hold for six months, the arithmetic favors the slow one by a wide margin.

Why Real Loss Does Not Match the Arithmetic

The calculator's own last line says the curve will bend. This section is what that sentence is hiding, because the gap between the projection and the scale is the reason most people conclude the deficit "stopped working".

The 3,500-calorie rule and its expiry date

Wishnofsky's 1958 paper is the source of the 3,500-calories-per-pound figure, and it holds up reasonably well for the first few weeks. It fails over months for one structural reason: it treats your energy expenditure as a constant, when expenditure falls as body mass falls.

The practical translation is simple. A 500-calorie deficit does not produce 52 pounds in a year. It produces close to a pound a week at first and progressively less thereafter, and the 26-week column in the projection table above should be read as an optimistic ceiling.

Thomas and colleagues put it bluntly in a 2013 commentary in the International Journal of Obesity, writing that the 3,500-kcal rule grossly overestimates actual weight loss, and demonstrating the gap against seven experiments in which intake was supervised or objectively measured. Hall and colleagues' 2011 modelling paper in The Lancet describes the real dynamics: body weight responds to a change in energy intake slowly, with a half-time of about one year, and people carrying more body fat lose more weight for the same change in intake.

Water, glycogen, and the first two weeks

Early loss usually beats the prediction, which sets up the disappointment that follows. Glycogen is stored with water, so any real cut in food — especially in carbohydrate — drops several pounds in the first week or two that have nothing to do with fat. The same mechanism runs in reverse on a single high-carbohydrate day, which is why the scale can rise two pounds overnight while you were still in a genuine deficit.

Weigh daily under the same conditions, average each week, and compare weekly averages rather than individual mornings. A single reading is mostly hydration, sodium and gut contents; a four-week trend is mostly fat.

Your maintenance falls as you do

This is the effect that silently closes a deficit, and it is pure arithmetic rather than anything mysterious. Take a 30-year-old man, 5 ft 10 in, moderately active, and run his TDEE at each weight on the way down. If he sets his target once at 220 pounds and never revisits it, this is what the same intake is worth:

He set out to lose a pound a week and, forty pounds later, is running a deficit worth about a sixth of a pound a week — without changing a single thing about how he eats. Nothing went wrong; he is simply a smaller man now, and a smaller man costs less to run.

The same effect moves the flags. A 35-year-old woman, 5 ft 4 in, lightly active, has a maintenance of 2,058 at 180 pounds, so the standard rate returns an unflagged 1,558. At 160 pounds her maintenance is 1,933 and the same rate returns 1,433 with a note; by 130 pounds it is 1,746, and even the gentle rate returns 1,496 with a note. The last stretch is always the hardest, and this is the reason why.

Metabolic adaptation, in proportion

On top of the arithmetic there is a genuine biological effect: resting metabolism falls by more than body composition alone predicts, and spontaneous movement drops when energy is scarce. The most-cited measurement of the extreme end is Fothergill and colleagues' 2016 follow-up of "The Biggest Loser" competitors, who lost 58.3 kg on average over 30 weeks and whose resting metabolic rate fell by 610 kcal a day. Six years later it was still 704 kcal a day below baseline, with 499 of that unexplained by their body composition.

That is a 30-week competition with extraordinary deficits, not a template for someone eating 2,000 a day, and quoting it as what awaits anyone who diets would be dishonest. The transferable lesson is directional: adaptation is real, it scales with how hard and how fast you push, and it is an argument for the slower option rather than a reason to avoid deficits.

How often to re-run the numbers

Every four to six weeks, or after about 10 pounds of change, whichever arrives first. Recalculate maintenance at your current weight, then bring the new figure back here and re-select your rate. Skipping this step is the single most common reason a plan that worked for six weeks does nothing in week ten.

If the weekly average has been flat for three weeks at what you believe is a deficit, the honest conclusion is that intake and expenditure are now equal — whatever the calculator says. The fix is a smaller target or more movement, not a friendlier estimate of maintenance.

Recompute maintenance at your new weight with the TDEE Calculator.

Holding the Deficit Without Losing Muscle

A calorie target says nothing about what the calories are made of, and the composition decides how much of the weight you lose is fat. Two things do most of the work here, and neither is complicated.

Protein and resistance training

The 2017 Advances in Nutrition review by Cava, Yeat and Mittendorfer summarizes the evidence plainly: diet-induced weight loss reduces muscle mass, high protein intake helps preserve lean body and muscle mass during weight loss, and both endurance and resistance training help preserve muscle — with resistance training also improving strength. That is the whole intervention. Eat enough protein, keep lifting, and a larger share of what leaves is fat.

How much protein depends on who you are. Helms and colleagues' 2014 systematic review of energy-restricted, resistance-trained athletes concluded their needs are likely 2.3 to 3.1 g per kg of fat-free mass, scaled up with the severity of the restriction and how lean the person already is. Someone starting from a higher body-fat percentage, at a gentle deficit, needs considerably less than the top of that range.

For a gram target based on your own weight and training, use the Protein Calculator.

Spending a smaller budget

A 500-calorie deficit does not have to come entirely from the plate. Half from food and half from added movement leaves the eating target 250 calories higher for the same rate of loss, which is materially easier to live with — and it is the only lever that helps when a flagged target has nowhere left to fall.

Within the food half, the calories that go furthest are the ones attached to protein, fiber and volume, because they leave you less hungry at the end of the day than the same energy in liquid or refined form. That is a practical statement about appetite rather than a metabolic trick: the deficit is still doing the work.

To split the target into protein, carbohydrate and fat grams, take the number into the Macro Calculator.

Tracking honestly is the hard part

The most common reason a calculated deficit fails to show up on the scale is not metabolism, and there is a well-known measurement of it. Lichtman and colleagues studied people who reported eating under 1,200 kcal a day without losing weight, published in the New England Journal of Medicine in 1992, and measured their expenditure directly: it was within 5 percent of predicted. What was off was the reporting — the group underreported actual food intake by an average of 47 percent and overreported physical activity by 51 percent.

The lesson is not that people lie. It is that estimating portions by eye is genuinely hard, and the errors run in one direction. If your target is 2,000 and the scale has not moved in a month, weigh the food for two weeks before concluding anything about your metabolism.

Limits: When This Calculator Does Not Apply

This tool does one subtraction well. Being clear about what it is not doing is the difference between a useful planning number and a false sense of precision.

What the calculator does not know about you

• It has no body weight, sex, age or body-fat input. It cannot tell you whether your chosen rate is 0.4 percent or 1.6 percent of your body weight per week — the check in the rate table above has to be done by you.
• It does not update as you lose. The result is a snapshot at the maintenance figure you typed; bring a fresh TDEE every four to six weeks.
• It does not model adaptation. The weekly shortfall is a straight multiplication by seven, so the longer the horizon, the more the projection overshoots.
• The accepted input range is not an endorsement. Enter the floor of 1,200 maintenance with any rate and the tool still calculates — 1,200 at the standard rate returns 700 kcal/day — with the warning attached. The warning is the operative part of that output.
• It knows nothing about food. Two people eating identical calorie targets can have completely different outcomes for protein intake, satiety and how much muscle they keep.

Who should not plan from a general deficit target

Nothing on this page is medical advice, and the calculator has no way to know which of the above applies to you. If you are planning a large change, or any change alongside a health condition, take the number to a physician or a registered dietitian and let them adjust it.

• Anyone pregnant or breastfeeding. Both add requirements rather than subtract them, and the figures belong to a clinician working from current guidance.
• Children and teenagers, who are still growing and whose intake should not be set by an adult maintenance equation.
• Anyone with a history of disordered eating, for whom calorie targets and daily weighing can do more harm than the weight itself.
• People managing diabetes, taking insulin or other medications with a food-timing component, or living with kidney, liver or thyroid conditions — the deficit interacts with the treatment.
• Anyone already at or below a healthy weight for their height, where the honest answer to "what deficit should I run" is none.