Calorie Deficit Calculator
Find the daily calories you need to lose weight
📉 Your details
0.5 / 1 / 2 lb per week corresponds to a roughly 250 / 500 / 1,000 kcal daily deficit.
Last updated June 2026
Method: Maintenance calories (TDEE) use the Mifflin-St Jeor BMR equation times a standard activity factor. The daily target subtracts your chosen deficit, and the timeline uses the widely cited ~3,500 kcal per pound of fat.
Included: Daily calorie target, deficit size, expected weekly loss, a week-by-week timeline to your goal weight, and a comparison table for 0.5 / 1 / 2 lb-per-week rates. Imperial (lb, ft/in) and metric (kg, cm) units.
Not included: Macronutrient splits, exercise calories you log separately, medical conditions and medications, and adaptive metabolic changes over time. This is an estimate, not medical advice - consult a doctor or registered dietitian before changing your diet.
Calorie deficit calculator: how to lose weight with numbers
Take a 32-year-old woman who is 5'5" and weighs 170 lb with a lightly active lifestyle. Her resting metabolism (BMR) works out to about 1,482 calories, and multiplying by a 1.375 activity factor gives a maintenance level (TDEE) of roughly 2,037 calories per day. To lose about 1 pound a week she subtracts a 500-calorie deficit, leaving a daily target near 1,537 calories. If her goal is 150 lb - 20 pounds away - that pace reaches the goal in about 20 weeks, or just under five months. This calorie deficit calculator runs exactly that math for your own stats.
How the calorie deficit is calculated
First the tool estimates your maintenance calories, then subtracts the deficit you pick:
Daily target = (BMR × activity factor) − daily deficit BMR uses the Mifflin-St Jeor equation: 10 × kg + 6.25 × cm − 5 × age, then +5 for men or −161 for women. The activity factor (1.2 sedentary to 1.9 extra active) turns BMR into TDEE. Your weekly loss is the deficit times seven, divided by about 3,500 calories per pound of fat - so a 500-calorie deficit is roughly 1 lb/week, and 1,000 is roughly 2 lb/week.
How fast should you lose weight?
A steady, sustainable rate is usually best. The three preset rates map to clear deficits:
- 0.5 lb/week - a gentle 250-calorie deficit, easiest to maintain and protect muscle.
- 1 lb/week - the standard 500-calorie deficit, a good balance of speed and adherence.
- 2 lb/week - an aggressive 1,000-calorie deficit, best suited to people with more weight to lose and only for short stretches.
The calculator floors your target at about 1,200 calories/day for women and 1,500 for men and warns you when a chosen rate would push below that, because very-low-calorie diets are hard to sustain and risk nutrient and muscle loss.
Why the scale slows down
The "3,500 calories = 1 pound" rule is a useful starting point, not a law. As you get lighter your body burns fewer calories, so a fixed intake produces a smaller deficit and weight loss tapers - a normal effect called adaptive thermogenesis. Water weight, sodium and glycogen also swing your scale day to day. The fix is simple: recalculate every few weeks at your new weight, and track 2-3 week averages instead of reacting to a single morning's reading.
Keep the weight you lose as fat
To make sure most of the loss is fat rather than muscle, eat enough protein (roughly 0.7-1 g per pound of goal body weight) and include resistance training. Combine the calorie target here with our Macro Calculator for a protein/carb/fat split, dial in a daily gram goal with the Protein Calculator, and use the TDEE Calculator if you want to double-check your maintenance number.
How to use this calculator
You only need a handful of numbers to get a realistic target. Work through the fields in order:
- Units: choose imperial (lb, ft/in) or metric (kg, cm) - the math is identical, only the display changes.
- Age, sex, height and current weight: these feed the Mifflin-St Jeor BMR equation, which estimates the calories your body burns at complete rest. (You can isolate that resting number with the standalone BMR Calculator.)
- Activity level: pick the option that honestly matches a normal week, from sedentary (desk job, little exercise) to extra active (hard physical job or daily training). This turns your BMR into your maintenance calories (TDEE).
- Goal weight: enter the weight you want to reach so the tool can build a week-by-week timeline.
- Loss rate: choose 0.5, 1, or 2 lb per week. The calculator converts this into a daily deficit and subtracts it from your maintenance calories.
The result updates instantly. Read your daily calorie target at the top, then check the deficit size, expected weekly loss, and the estimated number of weeks to your goal. If a warning appears, your chosen rate would push your intake below a safe floor - slow the pace down.
Who this calculator is for
This tool is built for anyone who wants to turn "I want to lose weight" into a concrete daily number. That includes:
- First-time dieters who need a realistic calorie target instead of guessing or starving.
- People hitting a plateau who want to recalculate their deficit at a lower body weight.
- Gym-goers in a cut trimming body fat while trying to hold onto muscle.
- Meal planners and calorie trackers who want a daily budget to build their food log around.
- Anyone setting a goal date - a wedding, vacation or check-up - who wants to see whether their target weight is realistic in the time they have.
It is not intended for children and teens, pregnant or breastfeeding people, or anyone with an eating disorder or a medical condition affecting weight - those situations need professional guidance, not a generic formula.
A second worked example: a man losing 2 lb per week
Take a 40-year-old man who is 5'10" and weighs 220 lb with a moderately active routine. His BMR is roughly 1,914 calories, and a 1.55 activity factor puts his maintenance (TDEE) near 2,967 calories per day. Choosing an aggressive 2 lb/week pace means a 1,000-calorie deficit, leaving a daily target of about 1,967 calories - still comfortably above the male floor. With a goal weight of 190 lb (30 lb away), that pace reaches the goal in about 15 weeks. Notice that because he is larger and more active, a 1,000-calorie deficit still leaves him plenty of food, whereas a smaller, less active person would hit the safe floor long before a 1,000-calorie cut.
Key terms explained
- BMR (basal metabolic rate): the calories your body burns at complete rest just to keep you alive - breathing, circulation, organ function. It's the biggest single chunk of your daily burn.
- TDEE (total daily energy expenditure): your maintenance calories - BMR plus the energy used by movement, digestion and exercise. Eat at your TDEE and your weight holds steady.
- Calorie deficit: the gap between what you eat and your TDEE. A negative balance is what drives fat loss.
- NEAT (non-exercise activity thermogenesis): calories burned through everyday movement like walking, fidgeting and chores. It varies a lot between people and tends to drop when you diet, which is one reason progress slows.
- Adaptive thermogenesis: the metabolic slowdown that happens as you lose weight and eat less, making the same intake produce a smaller deficit over time.
- Maintenance calories: the intake that keeps your weight stable - the same as TDEE, and the number you switch to once you reach your goal.
What changes your daily target
If you change the inputs and watch the number move, a few factors clearly dominate:
- Body size: heavier people and taller people burn more at rest, so their maintenance - and therefore their target - is higher.
- Activity level: moving from sedentary (1.2) to very active (1.725) can swing your maintenance by 500-800 calories. Be honest here; overestimating is the most common error.
- Chosen loss rate: each step up (0.5 to 1 to 2 lb/week) subtracts another 250-500 calories from your target.
- Age and sex: BMR falls slowly with age, and the equation adds for men and subtracts for women, so an older woman will have a lower target than a younger man of the same weight.
- Muscle mass: the formula uses total weight, but in reality more muscle raises your burn - one reason resistance training helps long term.
Tips to make the deficit stick
The best deficit is the one you can actually maintain. A few habits make a target far easier to hit week after week:
- Lead with protein and fiber: both are filling, so you feel satisfied on fewer calories and protect muscle at the same time.
- Watch liquid calories: sodas, juices, alcohol and creamy coffees add up fast and don't fill you up - an easy first place to cut.
- Build the plate around volume: vegetables, broth-based soups and whole fruit let you eat a large, satisfying amount for few calories.
- Plan, don't wing it: deciding meals ahead of time beats willpower in the moment, when you're hungry and tired.
- Allow flexibility: a target you hit five or six days out of seven, with a planned higher day, beats a perfect plan you quit. Consistency over weeks matters more than any single day.
Limitations and assumptions
This calculator is a planning estimate, not a precise prescription. Keep these assumptions in mind:
- BMR formulas like Mifflin-St Jeor are population averages - your real maintenance can differ by a few hundred calories in either direction.
- The 3,500 kcal = 1 lb rule is a simplification; real loss includes water and glycogen and slows as your metabolism adapts.
- The timeline assumes you hit your target consistently and that your maintenance stays constant, when in reality it falls as you get lighter.
- It uses total body weight, not body composition, so very muscular or very lean people may need to adjust.
- It does not account for medical conditions, medications, thyroid issues or hormonal changes that affect weight.
How it compares to related calculators
This page answers "how many calories should I eat to lose weight?" If your question is a bit different, a sister tool fits better:
- To find your maintenance number on its own, use the TDEE Calculator.
- To turn your target into grams of protein, carbs and fat, use the Macro Calculator.
- To plan a specific goal and date in more detail, use the Weight Loss Calculator.
- For a simple maintenance estimate without a goal, use the Calorie Calculator.
- To check whether your goal weight sits in a healthy range, use the BMI Calculator.
Sources
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), NIH - Weight Management.
- National Heart, Lung, and Blood Institute (NHLBI), NIH - Aim for a Healthy Weight.
- Centers for Disease Control and Prevention (CDC) - Losing Weight: a healthy, sustainable pace.
- U.S. Department of Agriculture & HHS - Dietary Guidelines for Americans.
⚠️ Common mistakes & edge cases
Cutting calories too aggressively
A bigger deficit feels faster but backfires: hunger, fatigue, muscle loss and a near-certain rebound. Most people do better with a 500-calorie deficit they can hold for months than a 1,200-calorie crash diet they quit in two weeks.
Forgetting that your TDEE drops as you lose
Your maintenance calories fall as you get lighter, so a deficit set at 170 lb is smaller at 150 lb. If progress stalls, recalculate at your new weight rather than slashing food further.
Double-counting exercise calories
The activity factor already includes your typical workouts. Eating back the calories a fitness tracker says you burned often erases your deficit, since those estimates run high. Pick the activity level honestly and leave it.
Reading too much into daily scale swings
Water, salt and digestion can move the scale 2-4 lb overnight with zero fat change. Weigh yourself the same way each morning and judge the weekly average, not isolated readings.
❓ Frequently asked questions
What is a calorie deficit?
A calorie deficit means eating fewer calories than your body burns each day. When you consistently take in less energy than you expend (your TDEE), your body makes up the difference by using stored energy - mostly body fat - which is what causes weight loss.
How big should my calorie deficit be to lose weight?
A common, sustainable range is a 250-1,000 calorie daily deficit. About 250 calories/day targets roughly 0.5 lb per week, 500 calories/day targets about 1 lb per week, and 1,000 calories/day targets about 2 lb per week. Faster isn't always better - larger deficits are harder to stick to and can cost you muscle.
How is the daily calorie target calculated?
The calculator estimates your maintenance calories (TDEE) using the Mifflin-St Jeor BMR equation multiplied by an activity factor, then subtracts your chosen daily deficit. For example, a TDEE of 2,037 minus a 500-calorie deficit gives a target of about 1,537 calories per day.
How many calories are in a pound of fat?
Body fat stores roughly 3,500 calories per pound. That's why a 500-calorie daily deficit (3,500 per week) is often used as a rule of thumb for losing about one pound of fat per week. It's an approximation - real-world loss varies with water weight, glycogen and metabolic changes.
Why isn't my weight loss matching the prediction?
The 3,500-calories-per-pound model is a simplification. As you lose weight your TDEE falls, so the same intake produces a smaller deficit over time (adaptive thermogenesis). Day-to-day water and sodium swings also mask fat loss. Recalculate every few weeks and judge progress over 2-3 week averages, not single days.
What is the lowest number of calories I should eat?
Most health authorities advise not dropping below about 1,200 calories/day for women or 1,500 for men without medical supervision, because very-low-calorie diets risk nutrient deficiencies and muscle loss. This calculator floors your target at those values and flags when your chosen rate would go below them.
Will I lose only fat in a calorie deficit?
Not entirely. Weight loss includes water, glycogen and some lean tissue alongside fat. Eating enough protein (roughly 0.7-1 g per pound of goal body weight) and doing resistance training help you keep more muscle so that most of the weight you lose is fat.
Should I create the deficit by eating less or exercising more?
Both work, but most people get further by eating less, because it is far easier to skip 500 calories than to burn 500 through exercise (that's roughly an hour of running). The realistic approach is mostly diet for the deficit, with exercise added for muscle, fitness and appetite control rather than as the main lever. Just don't 'eat back' the calories your tracker says you burned - those estimates run high and can erase the deficit.
Can I lose weight in a calorie deficit without counting calories?
Yes. Counting is the most precise way to hit a target, but many people create a deficit by managing portions, filling half the plate with vegetables, prioritizing protein and fiber, and cutting back on liquid calories and ultra-processed snacks. Use this calculator to learn roughly how many calories you're aiming for, then use those habits to land near it without weighing every meal.
Does a calorie deficit work the same for everyone?
The principle - eat less than you burn - is universal, but the numbers are personal. Two people of the same weight can have maintenance calories that differ by several hundred per day because of muscle mass, age, genetics, hormones, medications and daily movement (NEAT). The calculator gives a solid starting estimate; treat the first 2-3 weeks of real-world results as your true calibration and adjust from there.
Will eating too few calories put my body in 'starvation mode'?
Not in the dramatic way the phrase suggests - you cannot gain fat from eating too little. What is real is adaptive thermogenesis: very low intake lowers your metabolism somewhat and triggers strong hunger, fatigue and muscle loss, which makes the diet hard to sustain and easy to rebound from. That's why a moderate deficit you can hold beats an extreme one you abandon.
How long should I stay in a calorie deficit?
Long enough to reach your goal, but it doesn't have to be continuous. Many people run a deficit for 8-12 weeks, then take a week or two at maintenance calories (a 'diet break') before resuming. Breaks can ease hunger and fatigue and make the overall plan more sustainable. Once you reach your goal weight, switch to your new, lower maintenance calories to hold the result.
Why did I gain weight overnight even though I was in a deficit?
Almost always water, not fat. A salty meal, extra carbs, a tough workout, hormonal shifts or simply undigested food can add 1-4 lb on the scale overnight with no change in body fat. Fat loss shows up gradually in the weekly average, so judge progress over 2-3 weeks rather than reacting to a single high reading.
💡 Good to know
A slower deficit usually wins
Research consistently finds that people who lose weight at a gradual, steady pace are more likely to keep it off than those who crash diet. A 500-calorie deficit you can hold for months beats an extreme cut you abandon in two weeks - and it protects more muscle along the way.
Don't go below the safe floor
Most health authorities advise against eating under about 1,200 calories a day for women or 1,500 for men without medical supervision, because very-low-calorie diets risk nutrient deficiencies and muscle loss. The calculator flags any rate that would push you below that line.
Recalculate as you shrink
Your maintenance calories fall as you lose weight, so a deficit set at your starting weight gradually becomes smaller. Re-run the calculator every 10-15 lb (or whenever progress stalls) so your target keeps pace with your new body.