Most people who search for a calorie deficit calculator want one plain answer: how many calories should I eat today? The catch is that the answer depends on your age, height, weight, how much you move and how quickly you want the weight to come off. Get one of those wrong and the plan either stalls or leaves you hungry and tired by Wednesday.

This free calorie deficit calculator does the sums for you. Type your details in kg, stone and pounds, or lb, pick a weekly pace or a goal date, and you get a daily calorie target, a safe rate of loss, a macro split and a week-by-week timeline. It works as a daily calorie deficit calculator and a goal planner in one. Use the tool above first, then read on if you want to understand what the numbers mean and how they were worked out.

What is a calorie deficit?

A calorie deficit simply means eating fewer calories than your body uses in a day. Your body is always burning energy. It keeps your heart beating and your brain running, digests your dinner, and carries you to the bus stop. The total is called your total daily energy expenditure, or TDEE. Eat less than that number and the body makes up the shortfall from its stores, mostly body fat, so your weight drifts down.

The size of the gap matters more than people expect. A small deficit is easy to live with but slow. A big one looks quick on paper, yet it tends to bring hunger, poor sleep, a short temper and a greater chance of losing muscle along with fat. Good plans sit in the sensible middle, and finding that middle for your own body is exactly what a calorie deficit calculator is for.

You can create a deficit by eating less, moving more, or a bit of both. The maths does not care which you choose, although most people find it easier to trim portions and add a daily walk than to try to out-train a big dinner. One more thing worth knowing: the scale measures everything, not just fat. Water, food still in your gut and stored carbohydrate all change your weight from day to day, which is why the first week of a new plan often shows a drop that does not repeat.

How to use this calorie deficit calculator

The calculator above looks simple, with a handful of boxes and two buttons, but there is a fair amount going on underneath. Here is every control in the order you meet it, and what each one does to your result.

Step 1: Choose your sex and units

Pick Male or Female first. The equations use a different constant for each, which changes your resting burn by about 166 calories a day for the same height, weight and age. Next to it you will find the unit switch: kg (with centimetres), stone (stone and pounds, with feet and inches) or lb (pounds, with feet and inches). Switch whenever you like. Anything you have already typed is converted for you, so there is no need to start again. In stone mode, put the pounds part between 0 and 13. If you have 14 lb or more, add it to the stones.

Step 2: Enter your age and height

The calculator is made for adults, so age runs from 18 to 100. Height can be anywhere from 120 to 230 cm (3 ft 11 in to 7 ft 7 in). In imperial mode you type feet and inches in two boxes, and decimals are fine for the inches.

Step 3: Enter your current and goal weight

Use a recent weight, ideally first thing in the morning before breakfast. Then enter the weight you want to reach. The tool accepts 30 to 300 kg (roughly 4 st 10 lb to 47 st 3 lb), and your goal must be at least 0.5 kg or 1 lb below where you are now. It also checks your BMI. If you are already under 18.5 it will stop and suggest talking to a doctor, because trying to lose more is not advisable. If your goal would land in the underweight range, you will see a warning rather than a block, so you can rethink the target.

Step 4: Pick your activity level

This box has a bigger effect on your result than almost anything else, and it is the one people most often get wrong. The calculator multiplies your resting burn by the number below.

Table 1: Activity levels and their multipliers

Be honest, and if you are torn between two levels, pick the lower one. Overestimating activity is the most common reason a plan stalls. The multiplier already includes the exercise you do on purpose, so you should not eat those calories back afterwards. If you swim regularly and want to see what a session is worth, our swimming calorie calculator gives a useful estimate to help you choose between Light and Moderate.

Step 5: Choose a weight-loss pace, or a goal date

The pace menu offers four settings: 0.25 kg (0.5 lb) a week, 0.5 kg (1 lb) a week, which is marked as the steady, recommended option, 0.75 kg (1.5 lb) and 1 kg (2 lb) a week. In lb and stone mode the labels switch to pounds. The fifth option, Reach my goal by a date, swaps the menu for a date picker. Choose any day from one week to three years away and the calculator works out the gentlest pace that still gets you there. If the date is too close to be done safely, it tells you the earliest realistic date instead of quietly giving you an unsafe plan.

Step 6: Open the advanced settings if you want more control

The slider button to the left of Reset opens a settings panel inside the calculator. You can leave everything at its default, which is perfectly fine, or adjust:

• BMR formula. Auto picks Mifflin-St Jeor, or Katch-McArdle if you enter body fat. You can also force Mifflin-St Jeor, revised Harris-Benedict or Katch-McArdle.
• Body fat %. Optional. Allowed range is 3 to 60% for men and 10 to 60% for women, based on the minimum essential fat the body needs.
• Protein. 1.6, 1.8, 2.0 or 2.2 grams per kilogram of body weight. The default is 1.8.
• Fat share. 20, 25, 30 or 35% of your calories. The default is 25%.
• Meals a day. From 2 to 5, used to split your calories and protein into per-meal figures.

Step 7: Press Calculate and read your results

Press Calculate (or just hit Enter) and the form is replaced by four tabs. Each one answers a different question.

• Plan. The ring shows the calories you should eat each day, with the pink-orange part showing the deficit as a slice of your maintenance calories. Beside it are your daily deficit, your loss per week and the total weight to lose. Below sit four tiles: maintenance calories (TDEE), resting burn (BMR) with the formula used, time to goal in weeks and days, and your goal date with your BMI at the start and at the goal. A bar underneath either confirms your pace is within safe guidelines or opens a short list of safety notes.
• Macros. Your protein, carbs and fat in grams, with calories and percentage for each, plus calories and protein per meal and a daily fibre target.
• Timeline. An animated line from today to your goal date, with check-ins every four weeks showing the weight you should expect and the calories to eat from that point.
• Paces. The four standard paces side by side, with the calories, time and finish date for each. Tap a row and the whole plan switches to that pace.

Three buttons sit under the results. Edit inputs takes you back to the form with your numbers still in place. Copy plan copies a short text summary you can paste into your notes or send to a friend. Reset clears everything.

Messages you might see

• Goal too close. Your goal must be at least 0.5 kg (1 lb) below your current weight.
• BMI below 18.5. The calculator will not build a loss plan for someone who is already underweight.
• Maintenance close to the safe minimum. If your estimated maintenance is within 100 calories of 1,500 (men) or 1,200 (women), a deficit is not advised.
• Date too soon. You will be shown the earliest realistic date at the safe minimum.
• Floor reached. The pace you chose would take you under the safe minimum, so your calories are held at that figure and the real pace is shown.

How the calculator works behind the scenes

There are three steps: estimate your resting burn, scale it up for your lifestyle, then take away a deficit that matches the pace you picked.

Step one: your basal metabolic rate

Your basal metabolic rate (BMR) is the energy your body uses at complete rest. The calculator offers three well-known equations.

• Mifflin-St Jeor is the default. Published in 1990 after researchers measured the resting energy use of 498 people, it works like this: 10 × weight in kg, plus 6.25 × height in cm, minus 5 × age, then plus 5 for men or minus 161 for women. A 2005 review by the Academy of Nutrition and Dietetics found it predicted resting metabolic rate within 10% of measured values more often than the other common equations.
• Revised Harris-Benedict dates from 1984 (an update of the 1919 original) and uses different coefficients for men and women. It usually gives a slightly higher figure.
• Katch-McArdle ignores height and age and uses lean body mass instead: 370 + 21.6 × lean mass in kg.

Step two: your maintenance calories

BMR is multiplied by your activity factor from Table 1 to give TDEE, the calories that hold your weight steady. If all you want is your maintenance figure, without a plan attached, our TDEE calculator shows it on its own with a bit more detail.

Step three: turning a pace into a daily target

A kilogram of body fat holds roughly 7,700 calories (the older figure of 3,500 calories per pound says the same thing). So the daily deficit is your chosen weekly loss multiplied by 7,700 and divided by 7. A pace of 0.5 kg a week means a deficit of 550 calories a day, and your target is maintenance minus 550.

Why we rebuild the plan every four weeks

Many simple calculators take the weight you want to lose, divide it by the weekly pace and give you a date. That ignores something real: a lighter body burns less. This calculator runs your plan day by day instead and recalculates your intake every 28 days from your new weight, so the pace you chose is the pace you actually keep. Because maintenance drops as you slim down, your calorie target steps down a little at each check-in, and your finish date comes out a touch later than the simple method would suggest.

Here are three worked examples, all at a steady pace and all produced by the calculator.

Table 2: Worked examples

The first is a man aged 30, 180 cm, going from 80 kg to 70 kg with light activity at 0.5 kg a week. The second is a woman aged 35, 165 cm, going from 72 kg to 62 kg, also light activity at 0.5 kg a week. The third is a woman aged 45, 5 ft 4 in, going from 14 st 2 lb to 11 st 7 lb with a desk job at 1 lb a week. Notice that the woman at 72 kg is told to eat noticeably fewer calories than the man at 80 kg. That gap is not unfairness; it comes from the lower resting burn the equations predict for women.

In that first example the calculator tells the man to eat 1,898 calories at the start, 1,871 at week 4, 1,844 at week 8, 1,817 at week 12 and 1,790 at week 16. The change at each step is small, which is why people rarely notice it, but over four months it adds up to about 100 calories a day.

How many calories deficit to lose weight?

The quick formula is this: weekly loss in kilograms equals your daily deficit multiplied by 7, divided by 7,700. The table does that sum for the deficits people ask about most.

Table 3: Calorie deficit and expected weight loss

For most people a deficit somewhere between 300 and 750 calories a day is the sweet spot. It is large enough to see the scale move within a few weeks and small enough that you can still train, work and think straight. A 500 calorie deficit, roughly 0.45 kg or 1 lb a week, is the figure you will see quoted most often, and it is the one behind the calculator's steady setting.

How much calorie deficit to lose 1kg a week?

To lose a full kilogram every week you would need a deficit of about 1,100 calories a day. That is a lot. For an average woman whose maintenance is around 1,900 to 2,000 calories, it would mean eating under 1,000 a day, which is below the safe floor. Larger people with a high maintenance can sometimes manage it for a short time, but even then it is the upper end of what is sensible. If the calculator shows an asterisk next to your calories at the 1 kg pace, that is exactly what has happened: it has capped your intake at the minimum and the real pace is lower.

What is a safe calorie deficit?

Public health guidance in most countries generally points to losing about 0.5 to 1 kg (1 to 2 lb) a week. Within that range, slower is usually kinder to your muscle, your mood and your chances of keeping the weight off. The calculator builds several checks around this advice.

Table 4: Safety limits built into the calculator

• Safe minimum calories. It will never plan below 1,500 a day for men or 1,200 for women. Very low calorie diets of 800 or fewer calories a day are for people with obesity under medical supervision, usually for no more than 12 weeks.
• Pace warning. You get a note if your weekly loss is above about 1 kg (2 lb) or above 1% of your body weight.
• Deficit size warning. You get a note if the deficit is more than 25% of your maintenance calories, because bigger cuts raise the odds of fatigue, hunger and muscle loss.
• Goal weight check. You are warned if your goal puts you in the underweight BMI range. If you want to see where you stand first, try our BMI calculator.

How many calories should I eat to lose weight?

Generic charts often quote round figures like 2,000 calories a day for women and 2,500 for men. Those are population averages for maintaining weight, not a target for losing it, and they are not really targets for you either. A 55-year-old with a desk job and a 25-year-old warehouse worker will land far apart, and so will you and the person next to you.

That is why the calculator starts from your own details instead of a round number. In the worked examples, the man eats 1,898 calories and the woman 1,396, both for the same steady loss of 0.5 kg a week. Neither is anywhere near the generic 2,000 or 2,500, and both are still above the safe minimum for their sex.

To make a figure like 1,900 less abstract, it helps to picture a day. A bowl of oats made with milk and a sliced banana comes to roughly 300 to 350 calories. A baked potato with beans and a little cheese is around 400 to 500. Chicken stir-fry with rice and plenty of vegetables might be 550 to 650, and a yoghurt and a piece of fruit in the afternoon adds another 200 or so. That is already close to 1,600 calories before you have thought about tea or coffee with milk, so a small treat still fits. Drinks are where plans quietly go wrong almost everywhere: a beer is typically 150 to 250 calories depending on size and strength, and a glass of wine is not far behind.

How long does it take to lose weight in a calorie deficit?

Divide the weight you want to lose by the weekly pace and you have a rough answer. The table shows it for common goals.

Table 5: Weeks needed at each weekly pace (simple estimate)

The calculator will often give a slightly longer answer than this table because it allows for your calories dropping as you get lighter. For the first worked example, simple division says 20 weeks for 10 kg at 0.5 kg a week, while the day-by-day plan says 21 weeks (144 days). The difference is small, but it grows for bigger goals, so trust the calculator's date over mental arithmetic.

The Paces tab puts the pace choices next to each other. Here is what it shows for the first example, the man going from 80 kg to 70 kg.

Table 6: Pace comparison for a man losing 10 kg

The asterisk on the 1 kg row shows the floor in action. He would need 1,100 fewer calories a day than his maintenance of 2,448, which would leave 1,348. The calculator holds him at 1,500 instead, so his real starting pace is a little under 1 kg a week. If you want to see what a loss means in percentage terms, our weight loss percentage calculator turns kilograms into a share of your starting weight.

Calorie deficit calculator with macros

Hitting a calorie number is only half the job. What the calories are made of decides how full you feel and how much muscle you keep. The Macros tab splits your daily target into protein, carbohydrate and fat.

• Protein comes first. The default is 1.8 g per kg of body weight, and you can pick anything from 1.6 to 2.2 g. This sits inside the range sports nutrition researchers recommend for people who are dieting and training. If your BMI is above 25, the calculator bases protein on a healthier reference weight rather than your full current weight, so you are not told to eat far more than you need. Protein is also capped at 40% of your calories.
• Fat is set as a share of calories, 25% by default, with 20 to 35% available. Fat at 9 calories per gram is the most energy-dense nutrient and carries essential vitamins.
• Carbohydrate is whatever is left. It fuels training and keeps you from feeling flat.
• Fibre is shown as a target of 14 g per 1,000 calories, in line with the figure used in US dietary guidelines.

This is what the Macros tab gives for the first worked example, a 1,898 calorie day for a man at 80 kg with the default settings.

Table 7: Macro split for a 1,898 kcal day

With three meals that works out at about 633 calories and 48 g of protein per meal, and a fibre goal of 27 g. Change the meals-a-day setting in the advanced panel and those per-meal numbers update straight away.

Calorie deficit calculator with body fat percentage

If you know your body fat percentage, the advanced panel lets you use the Katch-McArdle equation. Instead of guessing from age and height, it works out your lean mass (weight minus fat) and bases your resting burn on that. It tends to help most for people who are noticeably more muscular, or noticeably less muscular, than average for their size.

Here is how the two methods compare for a man aged 28, 175 cm, going from 95 kg to 75 kg at 0.5 kg a week with moderate activity and 28% body fat.

Table 8: Mifflin-St Jeor against Katch-McArdle

There is one behaviour worth understanding. With Mifflin-St Jeor the calories step down at every four-week check-in (2,378, then 2,348, then 2,318 and so on) because your body weight falls. Katch-McArdle depends only on lean mass, and the calculator assumes you keep your muscle while you lose fat. The target therefore stays at 2,314 throughout, and the Timeline tab explains this instead of showing a recalculation that would not happen. If you later re-measure your body fat and the figure has changed, simply run the calculator again with the new number.

A word of caution: handheld and bathroom-scale body fat readings can be out by several percentage points. If yours is only a rough guess, leave the formula on Auto without entering it, and stay with Mifflin-St Jeor.

Calorie deficit calculator goal date

Plenty of people do not start with a pace, they start with an event: a wedding, a holiday, a medical appointment. Choose Reach my goal by a date and the calculator works backwards.

Suppose a woman aged 35, 165 cm, light activity, wants to go from 72 kg to 65 kg in 16 weeks (112 days). The calculator finds that she needs a pace of about 0.45 kg a week, a daily deficit of around 494 calories and a target of 1,452 calories a day against a maintenance of 1,946. That is a gentle, realistic plan. If she asked for 8 weeks instead, the calculator would say the date is too soon and offer the earliest safe date, which in her case is 78 days away. That is a lot more useful than a plan that quietly drops her to 900 calories.

Calorie deficit calculator in stone and pounds

Stone and pounds (common in the UK and Ireland) are rarely offered by calorie calculators, which usually stick to kilograms or pounds alone. This one handles all three. Choose stone in the unit switch, then type the stones and the extra pounds in separate boxes. The pounds part stays between 0 and 13, because 14 lb makes another stone. Results appear in the same unit you chose. For quick conversions on their own, try our kg to stone and pounds converter.

Table 9: Stone, pounds and kilograms

One stone is 14 lb, or about 6.35 kg. Losing a stone at 0.5 kg a week therefore takes a little under 13 weeks, and losing a pound a week takes 14. Those are good numbers to keep in your head when a plan feels slow.

Tips for sticking to your deficit

• Weigh yourself once a week. Same day, same time, after the toilet and before food. Daily weights bounce around with water and will mislead you.
• Track honestly for two weeks. People usually underestimate portions, oils, drinks and the odd biscuit. A short stretch of careful logging teaches you more than months of guessing.
• Put protein in every meal. Eggs, Greek yoghurt, chicken, fish, beans and lentils all help you feel full on fewer calories.
• Lift something heavy twice a week. Strength training tells your body to hold on to muscle while the fat comes off.
• Do not ignore sleep. Short nights raise hunger and make late-evening snacks far harder to resist.
• Watch liquid calories. Juice, fancy coffees, squash with sugar and alcohol add up without filling you.
• Plan for weekends. If your Saturday regularly wipes out your Monday to Friday deficit, shave a little from the weekdays or lighten the weekend rather than quitting.
• Recalculate as you go. Run the calculator again every 4 weeks, or after about 5 kg of loss, using your new weight.

What no calorie deficit calculator can tell you

Every online calculator, ours included, gives an estimate. The equations come from studies of groups of people, and your own metabolism can sit 5 to 10% either side of the average. Hormones, medication, how much you fidget, how well you sleep and how active your job is all shift your real maintenance in ways a form cannot see. The 7,700 calories per kilogram rule is also a simplification, since the body adapts as weight comes off.

The practical answer is to treat the result as a well-informed starting point. Follow it for three to four weeks, watch the weekly average of your weight, and nudge your calories up or down by 100 to 150 if the trend is not what you expected. Used that way, a calculator saves you months of guesswork. Used as an exact promise, it will sooner or later disappoint you.

Frequently asked questions

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