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Calorie Deficit Calculator

Enter your age, gender, current weight, a target weight, your height, activity level, and a timeframe. This calculator goes beyond a single number: it sets your daily calorie target, projects your weight week by week, splits your intake into protein, carbs, and fat, compares two formulas, and holds your plan to a safe floor instead of letting it crash too low.

Enter your details and a target, then click Calculate to see your daily intake, a weekly weight projection, macros, and a realistic safety check

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How to Use the Calorie Deficit Calculator

1

Enter your age and gender

Type an age between 1 and 120 and pick a gender. The gender changes the formula constant used to find your resting burn.

2

Set the weight unit and enter your current and target weight

Tap kg or lb on the switch, then type your current weight and your target weight into the boxes below it. The target must be lower than your current weight.

3

Set the height unit and enter your height

Switch between cm and ft + in. For feet and inches, fill in both boxes, keeping inches below 12.

4

Choose your activity level

Pick the level that matches your typical week, because it decides the multiplier applied to your resting burn.

5

Pick a timeframe and click Calculate

Choose how quickly you want to reach your target. The tool works back from that deadline, then keeps your plan above a safe calorie floor.

6

Read your full result

See your daily calorie intake, a week-by-week weight projection, macros, two formula estimates, and a safety check on your target and plan.

A Safe, Personal Calorie Deficit Plan - With a Week-by-Week Projection

A calorie deficit is simply eating less energy than your body uses, so your body pulls the difference from stored fat. Most deficit tools stop at one daily number and leave you guessing how progress will look. This one builds a complete plan: it works out your resting burn, scales it to your activity, sets a daily intake that fits your target and deadline, projects your weight at checkpoints through the journey, splits your calories into protein, carbs, and fat to protect muscle, and will not let your intake fall below a sensible floor. Enter your details and you get a clear path to the target, not a single vague guess.

Your Daily Calorie Target and Your Deficit

The headline number in the result is the daily calories you should eat. It is your maintenance calories (your total daily energy expenditure) minus the daily deficit needed to reach your target by your timeframe. Since about 7,700 calories of stored energy equal one kilogram of body fat, the tool divides your total calorie gap by your deadline in days to find the daily deficit. The number above the hero shows both the intake and the deficit it creates, so you always know the gap you are cutting.

A Weekly Weight Projection You Can Follow

The distinctive feature of this tool is its projection. Instead of leaving you with a final target and a mystery in between, it shows your estimated weight at a series of checkpoints, such as the quarter, halfway, and end of your journey, labelled by week. From your current weight it applies a steady weekly loss based on your deficit and draws a simple path to your target. You can glance at any checkpoint and see roughly where you should be, which makes the plan much easier to track and adjust along the way.

Progress at a Glance

A compact grid under the projection sums up the essentials of your plan: your maintenance calories, the total weight left to lose, the exact daily deficit, and the estimated time it will take. Each card pairs with a short note, so the line between your current weight, your daily cut, and your finish line is always visible in one quick scan.

A Muscle-Sparing Macro Split

Losing weight does not have to mean losing muscle. The result splits your deficit intake into grams of protein, carbs, and fat, with protein given priority at about 35 percent of your total. Protein supplies about 4 calories per gram and the note reminds you to aim for at least 1.6 grams per kilogram of body weight. Keeping protein high while in a deficit helps your body burn fat rather than lean tissue, which is exactly what you want from a serious plan.

Two Formulas Compared

Your maintenance calories are estimated with the Mifflin-St Jeor equation, considered the most accurate for the general population, and also with the older Harris-Benedict equation. The result shows both side by side with a plain sentence stating how many calories apart they land. When the two agree closely you can trust the number; when they drift, it is a reminder to treat your target as a range and adjust with real-world results.

A Reality Check on Your Target

Worthwhile goals should sit inside a healthy band, so the tool also computes your healthy weight range from your height using body mass index cut-offs of 18.5 and 24.9. The result tells you plainly whether your target falls inside that band. A person 1.75 m tall sees a healthy band of roughly 56.7 to 76.3 kg. If your target sits far outside it, the tool flags it as worth reconsidering before you commit to an extreme goal.

A Safety Floor That Will Not Be Broken

Strongly aggressive plans fail and can do harm, so this calculator protects you from them. If your target timeframe would push your intake below about 1,200 calories for women or 1,500 for men, the tool holds your intake at that floor and recalculates how long your target actually needs. It then shows an orange guide explaining why the journey is slower than you asked and why that slower path protects your muscle and energy. The warning tone on the hero makes it immediately clear the plan has been adjusted for safety.

Full Transparency in the Details

Every result closes with a details panel showing the exact inputs used - your weight, height, age, gender, activity level, and the chosen formula - so you can always see where a number came from. No black box, no hidden steps, just your inputs turned into a clear plan you can trust and repeat.

This calculator is for informational purposes only and is not medical advice. Always consult a qualified healthcare professional about your nutrition and health, especially before starting a restricted diet.

Frequently Asked Questions

A calorie deficit means taking in fewer calories than your body burns in a day. Your body then makes up the difference from stored energy, mostly fat. This is the fundamental mechanism behind weight loss, no matter which diet style you follow.
The main result uses the Mifflin-St Jeor equation for your resting burn, scaled by an activity multiplier for your total daily energy expenditure. A Harris-Benedict estimate is shown alongside it so you can judge how much the two formulas agree.
The tool divides your total calorie gap by your deadline to find a daily deficit, converts that into a steady weekly loss, and then draws your weight at a series of checkpoint weeks from start to target. It is a smooth best-case path, not a guarantee that every week will be identical.
If the plan required losing weight too fast for your timeframe, your intake would fall below about 1,200 calories for women or 1,500 for men. The tool caps the plan there and recalculates the real time needed, because eating less than that for long periods risks muscle loss, fatigue, and nutritional shortfalls.
Protein protects lean muscle while you are in a deficit. The split sets it at about 35 percent of your intake and the note suggests at least 1.6 grams per kilogram of body weight. Combined with strength training, eating enough protein helps you lose fat and keep the muscle you have.
It is the weight band that gives you a body mass index between 18.5 and 24.9 at your height. Use it as a reality check before committing to a target. If your goal falls well outside the band, it is worth reconsidering before making large diet changes.
The calculator is designed for adults. Children, teens, and people who are pregnant or breastfeeding have very different energy needs, and calorie restriction during pregnancy is not recommended. Consult a healthcare provider for personal advice in those cases.
As you lose weight, a lighter body needs fewer calories to maintain, so the same deficit gives you less. Prolonged restriction can also slow your metabolism beyond what your new weight predicts. Recalculate your plan for your new weight and consider periodic diet breaks, rather than cutting further.
Formula-based estimates are typically within about 10 percent of a lab measurement for most people. Muscle mass, hormones, sleep, and genetics all shift the real number, and real fat loss rarely follows a perfect straight line. Treat the figures as a starting point and adjust using your actual scale results over a few weeks.
No. Everything is calculated locally in your browser with plain JavaScript. Your age, gender, weight, and height are never stored, transmitted, or logged, and there are no cookies or data collection. Your privacy is fully protected.