Health calculator

Free calorie deficit calculator

Find the calorie deficit that loses weight at your pace. Enter your height, weight, age, activity level and how fast you want to lose, and the calculator returns the daily calories to eat, your maintenance (TDEE), the deficit, and weeks to your goal — updated live, as you type.

On this page15 sections

InputsLive

Units

Height

Weight

Age

Weekly loss target

lb/wk

Total to lose

Sex

Activity level

Result

Calories to eat per day

2,211 cal/day

Eat this to lose about 1 lb per week — a deficit below your maintenance calories.

Maintenance (TDEE)2,711 cal/day

Daily deficit500 cal/day

Time to goal10 weeks

Your plan

Maintenance calories (TDEE)	2,711 cal/day
Daily deficit	500 cal/day
Calories to eat	2,211 cal/day
Estimated weekly loss	1 lb/wk
Time to lose 10 lb	10 weeks

Activity: Moderate (×1.55). Real-world loss often runs slower than the 3,500-calorie rule predicts as your metabolism adapts.

Estimates only; individual metabolism varies and real loss often runs slower. Why is this an approximation?

Results are estimates. Consult a professional.

Definition

What is a calorie deficit?

A calorie deficit is simply eating fewer calories than your body burns. Your body covers that shortfall by tapping its energy stores — mostly body fat — and you lose weight. It is the one mechanism behind every diet that has ever worked: low-carb, keto, intermittent fasting, or plain calorie counting all succeed only insofar as they leave you in a deficit. This calculator finds the daily calorie target that puts you in one, starting from how many calories you burn in a day (your TDEE) and subtracting the deficit that matches your goal.

calorie deficit = calories burned (TDEE) − calories eaten

calories to eat = TDEE − daily deficit

TDEE = BMR × activity factor

Deficit vs surplus vs maintenance

Eat below your TDEE and you are in a deficit (you lose weight). Eat above it and you are in a surplus (you gain). Eat at it and you maintain. The calculator above shows your maintenance number and the deficit target side by side, so you can see exactly how far below maintenance you need to land.

How big

How much of a calorie deficit do you need to lose weight?

The benchmark comes from the 3,500-calorie rule: one pound of body fat stores roughly 3,500 calories, so a deficit of about 3,500 calories over a week loses about one pound. Spread across seven days, that is a deficit of 500 calories a day for 1 lb per week, or 1,000 a day for 2 lb per week. Most experts recommend a deficit of 300–500 calories per day as the sustainable sweet spot.

Daily deficit	Weekly loss	Best for
250 cal/day	≈ 0.5 lb/week	Gentle, easy to sustain, minimal hunger
500 cal/day	≈ 1 lb/week	The standard recommendation for most people
750 cal/day	≈ 1.5 lb/week	Faster loss with more discipline
1,000 cal/day	≈ 2 lb/week	The aggressive upper limit — not for everyone

Based on the 3,500-kcal-per-pound rule. Weekly loss = (daily deficit × 7) ÷ 3,500.

1–2 lb a week is the safe range

Going faster than 2 lb a week usually costs you muscle and water rather than extra fat, and it is hard to stick to. A smaller, steadier deficit almost always wins over the long run.

Method

How to calculate your calorie deficit

Working out your deficit is a three-step chain. The calculator does all three live, but here is what is happening under the hood:

Find your BMR. The Mifflin-St Jeor equation estimates the calories your body burns at complete rest, from your sex, age, height, and weight.
Multiply by your activity factor to get TDEE. An activity multiplier from 1.2 (sedentary) to 1.9 (athlete) scales BMR up to your real daily burn — your maintenance calories.
Subtract your deficit. Take 250–1,000 calories off TDEE depending on how fast you want to lose. The result is your daily calorie target.

This builds directly on the BMR calculator and the TDEE calculator — the deficit is just one subtraction on top of TDEE.

Worked example

A worked example using the calorie deficit calculator

Example: a 30-year-old man, 175 cm, 80 kg, wanting to lose 10 lb

Marcus is 30, stands 175 cm, weighs 80 kg, and has a moderately active job and gym routine. He wants to lose 10 lb at a sustainable 1 lb per week. Here is the arithmetic the calculator runs through, step by step.

Step 1 — Find his TDEE

His Mifflin-St Jeor BMR is about 1,749 cal/day. Multiplied by the moderately active factor of 1.55, his maintenance need (TDEE) is roughly 1,749 × 1.55 ≈ 2,711 cal/day.

Step 2 — Choose a deficit for the target loss rate

For 1 lb per week he needs a deficit of 500 cal/day (because 500 × 7 = 3,500 ≈ one pound). His daily target becomes 2,711 − 500 ≈ 2,211 cal/day — comfortably above the 1,500-calorie safe floor for men, so no clamping is needed.

Step 3 — Work out the timeline

Weeks to goal = (goal lb × 3,500) ÷ (deficit × 7) = (10 × 3,500) ÷ (500 × 7) = 35,000 ÷ 3,500 = 10 weeks.

Eat ≈ 2,211 cal/day → lose 10 lb in about 10 weeks

That is Marcus's plan: hold a 500-calorie daily deficit and he reaches his 10-pound goal in roughly ten weeks — on paper. The next section explains why the real-world number usually runs a little slower.

The rule

The 3,500-calorie rule — and why it's only an approximation

Almost every calorie-deficit tool, including this one, runs on the 3,500-calorie rule: since a pound of body fat holds about 3,500 calories, a 3,500-calorie deficit should burn off one pound. It is a useful planning rule of thumb — but it is an approximation, not a law, and it tends to overestimate how much you will actually lose over time.

The rule assumes your metabolism stays fixed while you diet. It does not. As researchers writing in the International Journal of Obesity put it, the 3,500-kcal rule "grossly overestimates" real weight loss because it ignores the physiological changes that come with losing weight. A smaller body burns fewer calories, so the same 500-calorie deficit shrinks in effect as the months pass — which is why a straight-line prediction always looks faster than the scale.

Treat the timeline this calculator gives you as a best-case estimate. Expect real loss to track close to the prediction for the first few weeks, then gradually fall behind it. Adjust against what the scale actually does over 2–3 weeks rather than trusting the formula to the day.

Plateaus

Why weight loss slows down (adaptive thermogenesis)

If your loss stalls even though you are still eating in a deficit, the usual culprit is adaptive thermogenesis — the drop in energy expenditure that is larger than the drop you would expect from losing weight alone. Your body reads prolonged calorie restriction as a threat and quietly dials down its energy use to defend its fat stores.

It works through several channels at once: active thyroid hormone (T3) falls, and NEAT — the calories you burn fidgeting, standing, and moving unconsciously — declines without you noticing. The effect is real and measurable: total energy expenditure can fall by roughly 15% after a 10% weight loss, and about 40% of that drop is adaptive thermogenesis rather than simply being a smaller body.

Keep the deficit moderate. Research suggests using the smallest deficit that still moves the scale — roughly 20–25% below maintenance — to limit metabolic slowdown.
Recalculate as you lose. Your TDEE falls with your weight, so update your numbers every 4–5 kg (10 lb) instead of holding an old target.
Protect muscle. Enough protein and some resistance training preserve lean mass, which keeps your resting burn higher.
Consider diet breaks. Short periods at maintenance can ease the hormonal and adherence pressure of a long diet.

Diet vs exercise

Calorie deficit through diet vs exercise

You can create a deficit by eating less, by moving more, or by both. The math is identical — a 500-calorie deficit is a 500-calorie deficit however you get there — but the practicalities are not. Diet is the more reliable lever for most people: it is far quicker to skip a 500-calorie snack than to burn 500 calories, which can mean an hour of hard exercise.

Diet — the fastest, most controllable way to open a deficit. Small swaps add up quickly and don't depend on finding time to train.
Exercise — burns extra calories, protects muscle in a deficit, and brings health benefits the scale never shows. But appetite often rises to partly offset it.
Both — the most sustainable mix for most people: a modest dietary cut plus activity you can keep up, so the deficit doesn't rely on either one alone.

To estimate the exercise side, pair this with the calories burned calculator; to plan the food side, the macro calculator turns your target into protein, carbs, and fat.

Safety

How low is too low? Safe minimum calories

A bigger deficit is not automatically better. Dropping intake too far backfires — you lose muscle alongside fat, your metabolism adapts harder, and hunger and fatigue make the diet impossible to sustain. For that reason this calculator floors your target at a safe minimum: about 1,200 calories a day for women and 1,500 for men.

Don't drop below the floor without guidance

If your goal would push your target under 1,200 (women) or 1,500 (men) calories, the calculator holds the target at the floor and your achievable deficit — and your weekly loss — simply become smaller. Eating below these levels for long should only be done under the supervision of a qualified nutrition professional.

Practically, this means a very small or very sedentary person can't safely lose at 2 lb a week — there just isn't enough room between their maintenance calories and the floor. In that case, lower your target loss rate, or add activity to widen the gap rather than starving the difference.

Calorie deficit calculator definitions

Eating fewer calories than your body burns in a day. The shortfall is covered by stored energy (mostly body fat), so you lose weight.

The total calories you burn in a day — BMR multiplied by an activity factor. This is your maintenance level: eat it and your weight holds steady.

The calories your body burns at complete rest just to stay alive. Estimated here with the Mifflin-St Jeor equation and used as the base for TDEE.

The rule of thumb that one pound of body fat equals about 3,500 calories, so a 3,500-calorie deficit loses roughly a pound. An approximation that overstates real-world loss over time.

The drop in energy expenditure during a diet that is larger than expected from weight loss alone — the body's defense against losing fat, and a key reason loss slows.

The lowest daily intake the calculator will recommend — about 1,200 calories for women and 1,500 for men — below which it caps the target.

Methodology

Sources and methodology

This calculator estimates maintenance calories with the Mifflin-St Jeor equation (the most accurate common predictive BMR formula per the American Dietetic Association) and standard activity factors, then applies a deficit using the 3,500-kcal-per-pound rule. The caveats above on metabolic adaptation reflect peer-reviewed critiques of that rule. All math runs in your browser; nothing you enter is stored or shared.

Mifflin MD, St Jeor ST, et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr (1990).Hall KD, Chow CC. Why is the 3500 kcal per pound weight loss rule wrong? Int J Obes (2013).NIDDK Body Weight Planner — on the limits of static calorie-deficit predictions.

Questions

Frequently asked questions about the free calorie deficit calculator

A calorie deficit calculator is a free online tool that helps you calculate the daily calorie deficit and target intake to lose weight at your chosen rate. TDEE minus a daily deficit; 500/day ≈ 1 lb/week via the 3,500 kcal/lb rule. Intake floored at a safe minimum. It runs entirely in your browser with instant results and no sign-up.

For healthy weight loss of about 1 pound per week, a calorie deficit of roughly 500 calories per day is enough. Doubling that to 1,000 a day targets about 2 lb per week — the safe upper limit for most people. Going lower than a safe minimum (about 1,200 calories for women, 1,500 for men) is not recommended.

To lose 1 pound of fat you need to burn about 3,500 calories, so at a 500–1,000 calorie daily deficit you should lose roughly 1–2 pounds in the first week. Early weeks often show a larger drop from water weight, and progress naturally slows as you get lighter.

Generally no. Most adults need a minimum of about 1,200 calories (women) or 1,500 calories (men) per day to meet basic nutritional needs. Eating below that risks muscle loss, nutrient deficiencies, and a sharper metabolic slowdown — this calculator floors your intake at the safe minimum.

Yes — research shows it's possible, especially for beginners, by combining a modest deficit with a high-protein diet and resistance training. It is slower than building muscle in a surplus, but the muscle you preserve keeps your metabolism higher while you lose fat.

For most people, yes. A 1,000-calorie daily deficit targets about 2 lb of loss per week — the safe upper limit — but it is hard to sustain and risks muscle loss and a sharper metabolic slowdown. A 300–500 calorie deficit is usually safer and more effective long term.

About

About this calorie deficit calculator

This calorie deficit calculator runs entirely in your browser. Your height, weight, age, and goal never leave your device — nothing is sent to a server, logged, or shared. It estimates your maintenance calories with the Mifflin-St Jeor equation and standard activity factors, subtracts the deficit that matches your target loss rate, floors your intake at a safe minimum, and converts the deficit to a timeline with the 3,500-calorie-per-pound rule — all updating instantly.

Calculators Cloud offers 400+ free tools with no sign-up. The whole Health calculators shelf includes TDEE, BMR, and Macros alongside this one. Or browse the full calculator directory.