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Calculator Answers

Calorie Deficit Calculator

Source: Wishnofsky M. Caloric equivalents of gained or lost weight. Am J Clin Nutr. 1958;6(5):542-546 · Source verified August 18, 2026

Blake Boege
Written by Blake Boege · Founder, Calculator Answers

A calorie deficit occurs when the number of calories consumed is lower than the total daily energy expenditure required to maintain current body weight. A calorie deficit calculator estimates the daily energy reduction needed to achieve a target weight by a specific date or at a chosen weekly weight loss rate. It performs two kinds of calculation. The day-to-day modes are exact subtraction against a maintenance figure the user supplies: intake gives the deficit, and a chosen deficit gives the intake. The goal-planning modes convert a weight difference into calories using the static historical figure of 3,500 per pound and divide by time, which is a rough scale rather than a prediction because energy needs fall as body mass falls. The calculator does not collect age, height or activity level, and does not decide what deficit is appropriate for anyone

Two of the four modes are plain subtraction against your maintenance estimate: intake gives you the deficit, and a deficit gives you the intake. The other two plan backwards from a goal weight, by date or by weekly rate, using a static historical conversion. The page keeps those apart because only one of them is exact.

See also: TDEE Calculator, BMR Calculator, and Calories Burned Calculator.

Quick Answer

Subtract intake from your maintenance estimate to get a daily deficit, or subtract a chosen deficit from maintenance to get the matching intake. Goal-planning modes work backwards from a target weight.

lb

e.g. 180

lb

Must be lower than current. · e.g. 160

cal

Use the TDEE calculator if unsure. · e.g. 2200

Goal planning uses the old static conversion of 3,500 cal per pound (7,700 cal per kilogram). That figure is a rough historical approximation, not a law: energy needs fall as body mass falls, so a fixed deficit produces less and less change over time. Treat the timeline as a rough scale, not a forecast.

Calorie deficit

Daily deficit

761 cal

Corresponding intake 1,439 cal/day

Weight to lose20 lb
Time frame92 days (~13.1 wk)
Total deficit70,000 cal
Daily deficit761 cal
Daily calorie target1,439 cal
Implied weekly rate1.52 lb/wk

A planning figure from the static 3,500 cal per pound conversion, not a forecast. Real weight change slows as body mass falls, so the same daily deficit produces less change month by month. For a model that accounts for that, see the NIDDK Body Weight Planner linked below.

Whether any particular intake or deficit is appropriate depends on the individual, and this page has no way to tell. That question belongs with a clinician or a registered dietitian.

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Examples

Maintenance 2,500, intake 2,000

500 cal daily deficit

Maintenance 2,500, deficit 500

2,000 cal intake

180 → 160 lb in 90 days, TDEE 2200

daily deficit 778 cal · intake 1,422 cal/day · 1.56 lb/wk

82 → 73 kg in 90 days, TDEE 2200

daily deficit 770 cal · intake 1,430 cal/day · 0.70 kg/wk

180 → 170 lb at 1 lb/wk

daily deficit 500 cal · ~70 days

How it works

Formula · daily deficit = estimated maintenance calories − intake; intake for a chosen deficit = maintenance − deficit

Two different kinds of calculation live on this page, and it is worth knowing which one you are looking at.

Day to day: exact arithmetic

daily deficit = maintenance estimate − intake

intake = maintenance estimate − chosen deficit

Nothing physiological is assumed. These are exactly as accurate as the two numbers you put in.

Goal planning: a static model

total = (current − target) × 3500 per lb, or × 7700 per kg

daily deficit = total ÷ days

This one does assume something, and the assumption is known to be wrong in the long run: that the calories-per-pound exchange rate holds steady while your body changes. Read the timeline as a rough scale, not a forecast.

A deficit is subtraction; a timeline is a model

The two day-to-day modes are exact arithmetic. Maintenance minus intake is the deficit, and maintenance minus a deficit is the intake that produces it. A maintenance estimate of 2,500 against an intake of 2,000 is a 500 calorie deficit, and asking for a 500 calorie deficit against the same maintenance returns an intake of 2,000. Neither answer depends on a model of the body.

The two goal-planning modes are different. They convert weight into energy using the old static figure of 3,500 calories per pound, which treats body tissue as a fixed fuel tank. Real bodies do not behave that way: as mass falls, the energy needed to carry and maintain it falls too, so the same daily deficit produces progressively less change. A timeline from this page is a rough scale, not a prediction, and the longer the horizon the looser it gets.

For a projection that models that slowdown instead of assuming it away, the NIDDK Body Weight Planner is the standard public tool. It is maintained by the National Institute of Diabetes and Digestive and Kidney Diseases and accounts for how energy needs shift as body weight and activity change. Verified 2026-08-15.

What this page will not do

  • It does not recommend a deficit. The values in the fields are starting points for modelling, not advice about what anyone should eat.
  • It does not judge whether an intake is safe. That depends on the individual and belongs with a clinician or a registered dietitian.
  • It does not promise a weight on a date. Every figure inherits the error in your maintenance estimate, in your intake logging, and in the static conversion itself.

Working it out by hand

Take a maintenance estimate of 2,400 calories per day. The two kinds of calculation on this page reach the same daily figure by different routes.

Deficit from intake, which is exact

  1. Subtract intake from maintenance: 2,400 − 1,900 = 500 calories per day.
  2. That is the whole calculation. No conversion, no timeline, and no assumption about the body: if the maintenance figure is right, the deficit is right.

By weekly rate, which is a model

  1. Weight difference: 190 lb to 176 lb is 14 lb.
  2. Convert to calories with the static figure: 14 × 3,500 = 49,000 calories in total.
  3. Convert the rate to days: 1 lb per week is 7 days per pound, so 14 lb takes 98 days.
  4. Divide: 49,000 ÷ 98 = 500 calories per day, and the corresponding intake is 2,400 − 500 = 1,900.

Both routes land on 500 and 1,900, which is what the calculator returns for these inputs. The difference is what the number means: the first is a subtraction that holds as long as the maintenance figure does, and the second carries an assumption about calories per pound that starts drifting the moment body mass changes.

Edge cases

  • The model does not update itself. The maintenance figure is held fixed across the whole timeline. Energy needs fall as body mass falls, so the real curve bends away from the straight line these modes draw, and the gap widens the further out the projection runs.
  • The two unit constants are not a matched pair. 3,500 per pound and 7,700 per kilogram are both conventional round numbers. Converted exactly, 3,500 per pound is about 7,716 per kilogram, so the same goal entered in pounds and in kilograms produces totals a fraction of a percent apart.
  • A rate in pounds is not a rate in kilograms. 1 lb per week works out to 500 calories per day; 1 kg per week works out to 1,100. Entering the same number after switching the toggle is a different request, not the same one in other units.
  • Empty and impossible inputs. The result panel stays blank rather than showing a placeholder. A target weight at or above the current weight, a date in the past, a non-positive rate, and a chosen deficit larger than maintenance each return their own message instead of a figure.

Your numbers stay in the page

Every figure you type is processed by this page in your browser. Your maintenance estimate, intake, weights and dates are not sent to a server, not stored after you close the tab, and not visible to anyone else. There is no account and nothing to sign up for.

Sources

The figure is cited here because it is what the calculator computes with, not as an endorsement of it. Later work has repeatedly shown that a fixed calories-per-pound exchange rate overstates long-run weight change, which is why the goal-planning modes are described on this page as a rough scale rather than a projection. The 7,700 per kilogram figure is the conventional metric round number rather than anything from the paper.

Related health calculators

What this page is. Subtraction, plus a rough static model behind the two goal-planning modes. It does not assess whether any intake or deficit is medically appropriate for you, and it holds no information about you with which to try. That judgement belongs with a clinician or a registered dietitian.

Disclaimer. Educational estimate only. This is not medical, nutrition, or weight-loss advice. Talk with a qualified health professional before making changes to your diet or weight plan.

Related Calculators

More tools from Health

TDEE CalculatorEstimate your Total Daily Energy Expenditure from sex, age, height, weight, and activity — with maintenance, cut, and bulk targets.BMR CalculatorEstimate your Basal Metabolic Rate — the calories your body burns at rest — using the Mifflin–St Jeor equation.Calories Burned CalculatorEstimate calories burned by activity using MET values, body weight, and duration. Common activity presets plus a custom MET option. Educational estimate, not a medical measurement.Protein Intake CalculatorWork out how much protein you need per day from body weight and goal. Shows an evidence-based range with its source, a planning target, grams per eating occasion, calories from protein, and how the 1 gram per pound rule compares.

Frequently asked questions

A calorie deficit happens when you consume fewer calories than your body uses. Over time, this gap pushes the body to use stored energy, which leads to gradual weight loss. The size of the deficit determines how quickly weight comes off.

This calculator does not decide that. It takes whatever deficit you enter and returns the arithmetic. What size is appropriate depends on your body, your health, what you are eating, what else is going on medically and what you are trying to achieve, none of which a subtraction can see. That question belongs with a clinician or a registered dietitian who knows your situation.

It is a historical approximation, not a law. Converting a weight difference into calories at 3,500 per pound (7,700 per kilogram) assumes the exchange rate never changes, and it does: energy needs fall as body mass falls, so a fixed daily deficit produces less change over time. The two goal-planning modes here use it because it is the conventional way to put a rough scale on a timeline, not because it predicts anything precisely.

Use the TDEE calculator on this site to estimate it from sex, age, height, weight and activity level, or enter a figure you already track. Every output on this page inherits the accuracy of that one number, so a maintenance estimate that is 200 calories out makes every deficit here 200 calories out too.

Deficit from intake and Intake for a deficit are exact subtraction against your maintenance estimate, and involve no model of the body at all. By target date and By weekly rate are different: they convert a weight difference into calories using the static 3,500 per pound conversion and divide by time, so they are rough planning estimates rather than projections.

Because the goal-planning modes hold your maintenance figure fixed while your weight changes. In reality a smaller body needs less energy, so the same daily deficit represents a shrinking gap as the weeks pass, and the real curve flattens against the straight line this page draws. Over a few weeks the difference is small. Over many months it is not, which is why the NIDDK Body Weight Planner exists.

From a 1958 paper by Max Wishnofsky in the American Journal of Clinical Nutrition, linked in the Sources section below. BE CLEAR ABOUT HOW WELL THIS PAGE KNOWS THAT PAPER: it is paywalled and we have not read it. The journal and its publisher both refuse an automated request, PubMed carries no abstract for it, and open-access indexes list it as closed with no readable copy anywhere. What this page can verify is how a later paper describes it. Hall, writing in the International Journal of Obesity in 2008, says the rule's origin "can be traced back to a calculation that assumes exclusive loss of adipose tissue consisting of 87% fat", citing Wishnofsky for it. So the 3,500 is a calculation resting on an assumption about what body weight is made of, not a measurement. This page previously said Wishnofsky reviewed the literature of the time; that was our own characterisation of a paper we could not open, no source supports it, and it has been removed. The two goal-planning modes use the figure because it is the conventional scale, not because it settles anything.

Because both figures are round numbers rather than a matched pair. A pound is 0.45359237 kg, so 3,500 per pound works out to about 7,716 per kilogram, not 7,700. The page uses the conventional round figure for each unit, which means the same goal entered in pounds and in kilograms produces totals that differ by a fraction of a percent. Against a 1958 population average, that gap is the smallest source of error here.

No, and the difference is large. At 3,500 per pound, 1 lb per week works out to 500 calories per day. At 7,700 per kilogram, 1 kg per week works out to 1,100 calories per day. A kilogram is about 2.2 pounds, so entering the same number in the other unit is a substantially different request. Check which unit the toggle is set to before reading the daily figure.

No. It holds the maintenance figure you entered fixed for the whole timeline. Energy needs fall as body mass falls, so the real curve flattens away from the straight line these modes draw. The model does not update itself, and the page has no way to know your weight has moved: it recomputes only from what is currently in the fields.

Deficit from intake and Intake for a deficit are subtraction against a number you supply, and they involve no model of the body at all: if the maintenance figure is right, the answer is exact. By target date and By weekly rate convert a weight difference into calories with the static conversion, then divide by time. The first pair is arithmetic. The second pair is arithmetic plus an assumption that does not hold indefinitely.

Because it holds no information with which to answer. The calculator collects a maintenance figure and either an intake, a chosen deficit, or a goal weight and a timeframe. It does not collect age, height, activity, medical history, medication, or anything about how you eat. A subtraction cannot see any of that, so naming a range here would be inventing an answer rather than computing one.

The result panel stays blank rather than showing a placeholder number. Non-numeric entries, zero and negative values, a target weight at or above the current weight, and a target date in the past each produce their own message instead of a figure. Nothing is assumed on your behalf when an input is missing.

Yes. It is free to use with no account, no sign-up, and no limit on calculations. Everything runs inside this page in your browser.