Calorie Deficit Calculator
HealthCalculate your daily calorie deficit from TDEE and project your expected weekly and monthly weight loss based on your target deficit size.
Gender
Age
yrs
1580
Weight
kg
30200
Height
cm
100250
Target Daily Deficit
kcal
1001000
Activity Level
Target Daily Calories
0
Maintenance TDEE
0
Projected Weekly Loss
0
Projected Monthly Loss
0
What is a Calorie Deficit?
The Calorie Deficit Calculator shows you exactly how many calories to eat per day to lose weight at your chosen pace, and projects how much weight you can expect to lose per week and per month at that rate. It starts by calculating your Total Daily Energy Expenditure (TDEE) using the Mifflin-St Jeor equation and your selected activity level, then subtracts your target daily deficit to arrive at a specific calorie number to aim for.
This tool goes a step further than a basic TDEE Calculator by directly modeling the weight loss outcome of your chosen deficit, using the standard approximation that roughly 7,700 kcal of cumulative deficit corresponds to about 1 kg of fat loss. Adjust the deficit slider to see how a more aggressive or more moderate approach changes your projected results.
How to use this Calorie Deficit calculator
- Select your Gender — Male or Female.
- Enter your Age, Weight, and Height using the sliders or number fields.
- Choose your Activity Level from the five options shown, matching your typical weekly exercise and movement.
- Adjust the Target Daily Deficit slider to set how aggressive or moderate your calorie reduction should be.
- Review your Target Daily Calories result, along with your maintenance TDEE and projected weekly and monthly weight loss.
- Recalculate every few weeks as your weight changes to keep your deficit and projections accurate.
Formula & Methodology
TDEE is calculated using the Mifflin-St Jeor equation and an activity multiplier:Men: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5 Women: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161 TDEE = BMR × Activity MultiplierTarget calories and weight loss projections follow:Target Calories = max(1,200, TDEE − Target Daily Deficit) Actual Deficit = TDEE − Target Calories Weekly Loss (kg) = (Actual Deficit × 7) ÷ 7,700 Monthly Loss (kg) = (Actual Deficit × 30) ÷ 7,700Worked example: A moderately active 30-year-old man weighing 80 kg and standing 170 cm tall has a TDEE of approximately 2,681 kcal/day. Choosing a 500 kcal/day deficit gives a target of 2,181 kcal/day, projecting a weekly loss of about 0.45 kg and a monthly loss of about 1.95 kg.
Frequently Asked Questions
A calorie deficit occurs when you consistently eat fewer calories than your body burns in a day (your TDEE), forcing your body to use stored fat for the remaining energy. This calculator subtracts your chosen deficit target from your calculated TDEE to give you a specific daily calorie number to aim for.
You choose a target deficit, but this calculator won't let your target calories drop below 1,200 kcal/day for safety, so your actual deficit may be smaller than requested if your TDEE is low. The step-by-step breakdown shows exactly how your target and actual deficit compare.
A commonly cited rule is that 7,700 kcal roughly equals 1 kg of body fat, so a 500 kcal/day deficit projects to about 0.5 kg (1.1 lb) of weight loss per week. This calculator applies that same conversion to your chosen deficit size to project weekly and monthly weight loss.
No — very large deficits (750+ kcal/day) often lead to faster initial weight loss but higher risk of muscle loss, fatigue, and difficulty sticking to the plan long term. A moderate deficit of 300-500 kcal/day is generally more sustainable and better preserves lean muscle mass during weight loss.
Your activity level determines your TDEE (Total Daily Energy Expenditure) baseline, which is the starting point before any deficit is applied. An inaccurate activity level — selecting Very Active when you're actually Lightly Active, for example — will make your target calories too high and slow your actual results.
The [TDEE Calculator](/tdee-calculator/) shows your maintenance calorie level without any weight loss goal applied. This Calorie Deficit Calculator builds on that same TDEE calculation but adds a deficit slider and projects your expected weekly and monthly weight loss, making it a more direct tool for active weight loss planning.
Yes — your TDEE decreases as your body weight decreases, since a smaller body generally burns fewer calories at rest and during activity. Recalculating every 2-4 weeks during a weight loss phase keeps your deficit and target calories accurate as your weight changes.
These projections are estimates based on population-average formulas and the standard 7,700 kcal-per-kg conversion — actual results vary due to water weight fluctuations, metabolic adaptation, and individual differences. Use the projection as a general guide and track your actual weight trend over several weeks for a more reliable picture.
This calculator caps your target calories at a 1,200 kcal/day minimum as a general safety floor, since going much lower risks inadequate nutrient intake and muscle loss. Very active individuals or those with higher TDEE should generally stay well above this floor even while in a deficit.
Higher protein intake during a calorie deficit helps preserve lean muscle mass while you lose fat, and also tends to improve satiety, making the deficit easier to sustain. Use the [Macro Calculator](/macro-calculator/) alongside your target calories here to set an appropriate protein target for your deficit.
No — the activity level you select already factors in your general daily movement and typical exercise routine, so you don't need to separately add back calories burned during workouts unless your activity varies significantly week to week. For day-specific exercise estimates, use the [Calories Burned Calculator](/calories-burned-calculator/).
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