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Calorie Deficit Calculator

Health

Calculate your daily calorie deficit from TDEE and project your expected weekly and monthly weight loss based on your target deficit size instantly.

Reviewed by the thecalcu.com team · Last updated July 13, 2026

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.

Why Use a Calorie Deficit Calculator?

Choosing an arbitrary calorie target without understanding the underlying deficit size makes it hard to predict, or trust, your expected results. This calculator connects your daily calorie target directly to a weekly and monthly weight loss projection, so you know upfront roughly what pace of progress to expect from your plan.

It's particularly useful for comparing deficit strategies: see how a moderate 300 kcal/day deficit compares to a more aggressive 750 kcal/day approach in terms of projected results, letting you choose a pace that's both effective and sustainable for your lifestyle.

Who Should Use This Calculator?

  • Anyone starting a structured weight loss plan who wants a specific daily calorie target rather than a rough guess.
  • People choosing between an aggressive and a moderate approach who want to see the weekly and monthly weight loss trade-off of each deficit size before committing.
  • Dieters plateauing on a current plan who want to recalculate their deficit as their weight and TDEE have changed.
  • Anyone tracking macros during a cut who needs a calorie target to feed into the Macro Calculator for protein, carb, and fat allocation.
  • People comparing calorie needs across formulas, best done alongside the Harris-Benedict Calculator for a cross-check.

What Insights Does the Calorie Deficit Calculator Give You?

  • Target Daily Calories, the primary result, your recommended daily calorie intake after applying your chosen deficit to your TDEE, capped at a 1,200 kcal/day safety minimum.
  • Maintenance TDEE, your estimated calorie burn at your current weight and activity level with no deficit applied, the baseline your target is calculated from.
  • Projected Weekly Loss, your estimated weight loss per week in kilograms, based on your actual daily deficit and the standard 7,700 kcal-per-kg conversion.
  • Projected Monthly Loss, the same projection extended to a full month, useful for setting realistic medium-term expectations.

Use the weekly and monthly projections to sanity-check your chosen deficit, if the pace looks too aggressive or too slow for your goals, adjust the deficit slider and see the targets update instantly.

How to use this Calorie Deficit calculator

  1. Select your Gender, Male or Female.
  2. Enter your Age, Weight, and Height using the sliders or number fields.
  3. Choose your Activity Level from the five options shown, matching your typical weekly exercise and movement.
  4. Adjust the Target Daily Deficit slider to set how aggressive or moderate your calorie reduction should be.
  5. Review your Target Daily Calories result, along with your maintenance TDEE and projected weekly and monthly weight loss.
  6. Recalculate every few weeks as your weight changes to keep your deficit and projections accurate.
Show formula & methodology ↓Show less ↑

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 Multiplier

Target 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) ÷ 7,700

Worked 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

What is a calorie deficit?
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.
How is my target daily deficit different from my actual deficit?
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.
How much weight will I lose per week?
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.
Is a bigger calorie deficit always better?
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.
Why does this calculator ask for my activity level?
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.
What is the difference between this calculator and the TDEE Calculator?
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.
Should I recalculate as I lose weight?
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.
Can weight loss projections from this calculator be trusted exactly?
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.
What's a safe minimum calorie intake while in a deficit?
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.
How does protein intake affect weight loss in a calorie 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.
Does a calorie deficit calculator account for exercise burned separately?
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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Also known as
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