Free online calorie deficit calculator

Calorie Deficit Calculator

Calculate your calorie deficit and get a daily calorie target for weight loss based on your age, sex, height, weight, activity level and desired weekly weight-loss rate.

Units
Sex used for the equation

This calculator uses the Mifflin-St Jeor equation and activity presets to provide a weight-loss estimate for adults. Individual energy needs and weight change can differ. It is not medical advice.

What is a calorie deficit?

A calorie deficit means eating less energy than your body uses over time. If estimated maintenance is 2,450 Cal/day and your intake is 2,150 Cal/day, the difference is a 300-Calorie daily deficit.

A calorie deficit calculator for weight loss estimates a daily calorie target from your energy needs and selected weekly rate. The result is an estimate, not a guarantee of a specific rate of weight loss.

How to calculate a calorie deficit

Your calorie target is built from three things: your estimated resting energy use, your activity level and the weekly weight-loss rate you choose.

  1. 1. Estimate resting energy (BMR)

    The Mifflin-St Jeor equation uses your age, sex, height and weight to estimate how much energy your body uses at rest.

  2. 2. Estimate maintenance calories

    Your BMR is adjusted for your activity level to estimate how much energy you use across a typical day.

    BMR × activity factor = estimated maintenance calories

    The activity factor depends on how active your typical week is across work, everyday movement and exercise.

    Mostly seated1.2
    Seated work and little walking, with little or no planned exercise.
    Lightly active1.375
    Mostly seated days, with regular walks or occasional light exercise.
    Moderately active1.55
    Regular walking or active daily routines, plus exercise on several days.
    Very active1.725
    Active days on your feet or frequent demanding workouts, with substantial movement outside training.
    Extremely active1.9
    Physically demanding days combined with frequent training, or similarly high activity across the week.

    These levels are practical guides, not fixed step-count or workout cutoffs.

    That is how maintenance calories determine your calorie deficit: they provide the reference point from which the deficit is subtracted. If you want to estimate maintenance calories or compare maintenance, weight-loss and weight-gain examples, use the Macroful Calorie Calculator.

  3. 3. Turn your weekly weight-loss rate into a daily calorie target

    The calculator converts the weekly rate you selected into an estimated daily calorie deficit, then subtracts that deficit from maintenance calories.

    Daily calorie deficit = weekly weight-loss rate (kg) × 7,700 Cal/kg ÷ 7 days

    Daily calorie target = estimated maintenance calories − daily calorie deficit

Example · 0.5 kg/week

0.5 kg × 7,700 Cal/kg ÷ 7 days ≈ 550 Cal/day deficit

If maintenance is 2,450 Cal/day: 2,450 − 550 = 1,900 Cal/day target

The 7,700 Cal/kg conversion is an estimate used to translate a weekly weight-loss rate into a starting calorie deficit, so actual weight loss can vary. The displayed calorie target is not shown below estimated BMR.

How many calories should I eat to lose weight?

There is no single calorie intake that makes everyone lose weight. Two people can choose the same weekly weight-loss rate and still get different daily targets because age, sex, height, weight and activity change estimated energy needs.

A weight loss calorie calculator is useful because it turns those personal inputs and your chosen weekly rate into a daily calorie target instead of giving everyone the same number.

Calorie deficit for different weekly weight-loss rates

Instead of asking you to choose an abstract calorie deficit, the calculator lets you choose a desired weekly rate of weight loss. It then converts that rate into an estimated daily deficit. Actual weight loss can be faster or slower.

0.5 kg/week≈ 550 Cal/day
0.75 kg/week≈ 825 Cal/day
1 kg/week≈ 1,100 Cal/day

Goal weight and estimated time

If you enter an optional goal weight, the calculator uses the difference between your current weight and goal weight together with the displayed daily calorie deficit to estimate how long it could take to reach that goal.

The estimated time is a calculation based on the displayed deficit, not a fixed prediction of when your weight will reach that value.

Why weight loss doesn't follow the calculator perfectly

A calculator can estimate energy needs, but it cannot predict day-to-day scale changes or guarantee that body weight will move at a fixed rate.

  • Water and stored carbohydrate: short-term changes can move scale weight without matching fat loss.
  • Activity varies: walking, training and everyday movement are not identical every day.
  • Energy needs change: as your body weight changes over time, your estimated daily energy needs can change too.
  • Actual calorie intake: portion sizes and logged amounts can differ from what you actually eat.

If your weight trend is flat or rising, use our guide to a calorie deficit that seems stuck to work through the scale trend, weekly intake and current maintenance estimate before changing your target.

For a faster way to keep that food log consistent, Macroful’s photo calorie counter lets you log a meal from a photo and review the result before saving it.

How to adjust your calorie target over time

Treat the calculated target as a starting estimate. Day-to-day weight is noisy, so one weigh-in is not enough to judge whether your calorie target matches your actual needs.

If your weight trend is not moving in the direction you expected, first check whether your logged portions and activity level still reflect your routine. If they do, recalculate your calorie target using your current weight. Only then consider a small adjustment instead of reacting to a single weigh-in.

How accurate is a calorie deficit calculator?

A calorie deficit calculator estimates energy needs; it does not measure them directly. The Mifflin-St Jeor equation estimates resting energy use from population data, and the activity factor adds another approximation. Your actual maintenance calories can therefore be higher or lower than the calculator’s estimate.

Formula source: original Mifflin-St Jeor study.

Frequently asked questions about calorie deficits

How do I stay in a calorie deficit?

Staying in a calorie deficit is mostly about consistency, not hitting your target perfectly every single day. Start with a realistic calorie target, log food as you eat rather than trying to remember everything at night, and keep a few repeatable meals that are easy to track. Checking portions and your intake throughout the day can also help you notice early when you are getting close to your target. A food-tracking app like Macroful can make that routine easier by letting you log meals with a photo, barcode, nutrition label, text AI or food search and compare your intake with your calorie target as you go.

Is a 1,000-calorie deficit too much?

A 1,000-Calorie daily deficit is a large reduction from maintenance and may be too aggressive for some people. Whether it makes sense depends on your estimated maintenance calories, body size and activity level. If the calculator gives you a calorie target very close to your estimated BMR, choose a slower weekly weight-loss rate and recalculate. A larger deficit is not automatically a better one.

Should I add exercise calories back when I’m in a calorie deficit?

Usually not if your usual workouts are already reflected in the activity level you selected. For example, if you chose an activity level that already represents your normal training and daily movement, adding those workout calories again can count the same activity twice. Keep your activity setting consistent and only update it when your routine changes meaningfully.

How long should I stay in a calorie deficit?

There is no fixed number of weeks that works for everyone. How long you should stay in a calorie deficit depends on whether your calorie target still fits your weight-loss goal, current body weight and usual activity. As your weight changes, your estimated calorie needs can change too, so recalculate your target periodically instead of using the same number indefinitely. If your progress changes noticeably, review your current inputs before making a large adjustment.

Is BMR the minimum number of calories I should eat?

No. BMR estimates how much energy your body would use at rest; it is not a recommended minimum calorie intake. In this calculator, Macroful uses estimated BMR only as a display floor so the calculated calorie target is not shown below that estimate. That is a calculator rule, not a personal medical recommendation or safety threshold.

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