Our free calorie deficit calculator uses the Mifflin-St Jeor equation, which research has found to be one of the most reliable formulas for estimating resting energy needs in healthy adults. It supports metric (kg and cm) and imperial (lbs and ft) units and shows your maintenance calories, daily deficit and calorie target side by side.

The results are estimates for healthy adults. If you are pregnant, breastfeeding, under 18, managing a medical condition or taking medication that affects weight, speak to a doctor or registered dietitian before changing how much you eat.

How the Calorie Deficit Calculator Works

First the calculator estimates your basal metabolic rate (BMR), the calories your body uses at rest, with the Mifflin-St Jeor equation:

• Men: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5
• Women: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161

Next it multiplies BMR by an activity factor to get your total daily energy expenditure (TDEE), then subtracts the deficit for your goal. For example, a 32-year-old man who is 175 cm tall, weighs 88 kg and is moderately active has a BMR of about 1,819 calories and a TDEE of about 2,819. A 500 calorie deficit gives a target of 2,319 calories a day.

Activity Levels and Weekly Goals

How to Use the Calorie Deficit Calculator

Follow these steps to get your number from the calorie deficit calculator.

Step 1: Enter Your Gender, Age, Height and Weight

Choose Metric or Imperial units, select Male or Female, and type your age, height and current weight.

Step 2: Pick Your Activity Level and Weight Loss Goal

Choose the activity level that matches a normal week, then select Maintain, Mild, Normal or Extreme weight loss as your goal.

Step 3: Read Your Daily Calorie Target and Deficit

Click Calculate. The tool shows your daily calorie target in large numbers, with your maintenance calories (TDEE) and the daily deficit underneath.

Step 4: Check the Safe Minimum Calorie Note

Read the note under the results. As a general guide, women should not go below about 1,200 calories a day and men below about 1,500 without medical supervision.

How Big Should Your Calorie Deficit Be?

A deficit of about 500 calories a day is a common starting point and leads to roughly 0.5 kg (1 lb) of weight loss a week for many people. Larger deficits can work for people with more weight to lose, but they are harder to sustain and can make it harder to get enough protein, fibre and vitamins.

Weight loss is rarely a straight line. Water, salt and hormones can move the scale up or down from day to day, so compare weekly averages rather than single weigh-ins.

Tips for Sticking to a Calorie Deficit

• Prioritise protein and vegetables, which help you feel full on fewer calories.
• Weigh or measure food for a week or two to learn real portion sizes.
• Keep strength training so more of the weight you lose comes from fat, not muscle.
• Recalculate with the calorie deficit calculator after every 4 to 5 kg lost, because a lighter body burns fewer calories.
• Sleep 7 to 9 hours; poor sleep makes hunger harder to manage.

Why Use a Calorie Deficit Calculator?

Guessing your calorie needs often leads to eating too little and feeling exhausted, or eating too much and seeing no progress. A calorie deficit calculator gives you a personalised starting number based on your body and lifestyle. Track your weight for two to three weeks, then adjust your intake by 100 to 200 calories if results are faster or slower than expected.

Frequently Asked Questions