Calorie Deficit Calculator

What is calorie deficit calculator?

A calorie deficit means eating fewer calories than your body uses. Over time, a steady deficit leads to weight loss. The size of the deficit decides how fast it happens, and a moderate deficit is easier to keep up than a drastic one.

This tool first estimates your maintenance calories using the Mifflin St Jeor equation and your activity level. It then subtracts the deficit that matches your weekly loss target and shows how long your goal may take.

How to use the calorie deficit calculator

1. Enter your sex, age, height, current weight and goal weight.
2. Choose your activity level and a weekly loss target.
3. Read your maintenance calories, daily target calories and the estimated weeks to reach your goal.

How the calorie deficit calculator works

Resting energy is 10 times weight in kg plus 6.25 times height in cm minus 5 times age, then plus 5 for men or minus 161 for women. Maintenance equals this value times the activity factor. A loss of one kilogram of body weight is estimated at about 7,700 calories, so the daily deficit equals the weekly loss target times 7,700, divided by 7.

Worked example

Common uses of the calorie deficit calculator

• Setting a starting calorie target.
• Checking if a weekly loss goal is realistic.
• Planning a timeline for a weight goal.
• Comparing slow and faster plans.
• Discussing a plan with a dietitian.

Tips and common mistakes

The 7,700 calorie rule is an average. Real weight loss slows as you get lighter, so treat the timeline as a guide.

Very low calorie plans can be unsafe. Talk to a doctor or registered dietitian before eating much less than your needs.

Track your weight weekly and adjust your target if the trend does not match your plan.

Background: what to know before you rely on it

Energy balance is the base of weight change. When intake is below expenditure, the body draws on stored energy. Maintenance estimates come from equations built on group averages, and individual needs can differ by several hundred calories. Because of this, the best plan is to start with an estimate, track results for two to four weeks and adjust. People with medical conditions, pregnant or breastfeeding women, teenagers and anyone with a history of disordered eating should seek professional guidance and not rely on a calculator.

Private, free and fast

This tool runs entirely in your browser. What you type or choose is not uploaded to a server and is not saved after you close the page, which keeps it fast and private. It is free to use as often as you like. See more in all calculators, or browse the full list of tools.

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Results are for information and education. For legal, financial, medical or security decisions, check with a qualified professional. Financial results are estimates and exclude fees and taxes unless the tool says otherwise.