How to Calculate Daily Calories — TDEE & Deficit

Introduction

Learning how to calculate daily calories is the cornerstone of achieving any body composition goal, whether it's weight loss, muscle gain, or maintenance. Your body operates on a simple principle of energy balance: calories in versus calories out. This guide will teach you how to find your Total Daily Energy Expenditure (TDEE)—the total number of calories you burn each day—and how to adjust it to create a safe calorie deficit for weight loss or a surplus for muscle growth. We'll break down the Mifflin-St Jeor equation, explain activity multipliers, and provide clear, step-by-step examples. By understanding these calculations, you can move away from guesswork and create a personalised, effective nutrition plan based on your body's specific energy needs.

What Is Total Daily Energy Expenditure (TDEE)?

Your Total Daily Energy Expenditure (TDEE) is the total number of calories your body burns in a 24-hour period. It's the sum of all the energy used for basic bodily functions, daily activities, and exercise. Knowing your TDEE is crucial because it represents your maintenance calories—the intake at which your weight remains stable. To lose weight, you need to consume fewer calories than your TDEE (a deficit). To gain weight, you need to consume more (a surplus). TDEE is not a static number; it changes with your weight, activity level, and other factors.

The Formula Behind the Calculator

The most accurate way to estimate your TDEE is to first calculate your Basal Metabolic Rate (BMR) and then multiply it by an activity factor.

Step 1: Calculate Basal Metabolic Rate (BMR)

Your BMR is the calories you burn at complete rest. The gold-standard formula is the Mifflin-St Jeor Equation:

• For Men: BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) + 5
• For Women: BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) - 161

Step 2: Apply an Activity Multiplier

Your activity level turns your BMR into your TDEE.

| Activity Level | Description | Multiplier | | :--- | :--- | :---: | | Sedentary | Little or no exercise | BMR × 1.2 | | Lightly Active | Light exercise 1-3 days/week | BMR × 1.375 | | Moderately Active | Moderate exercise 3-5 days/week | BMR × 1.55 | | Very Active | Hard exercise 6-7 days/week | BMR × 1.725 | | Extremely Active | Very hard exercise & physical job | BMR × 1.9 |

The Final Formula: TDEE = BMR × Activity Multiplier

How to Calculate Your Calorie Needs Manually

Follow these steps to calculate your personalised calorie targets.

Step-by-Step Guide

1. Convert Your Measurements. You need weight in kilograms (kg) and height in centimetres (cm).
   • Weight in kg = Weight in pounds ÷ 2.2
   • Height in cm = Height in inches × 2.54
2. Calculate Your BMR. Use the Mifflin-St Jeor formula for your sex.
3. Select Your Activity Multiplier. Be honest and objective about your typical week's activity, not your best week.
4. Calculate Your TDEE. Multiply your BMR by the multiplier. This is your maintenance calories.
5. Apply Your Goal Adjustment.
   • Weight Maintenance: Calories = TDEE
   • Weight Loss (Fat Loss): Calories = TDEE - 500 (for ~0.5kg/1lb loss per week)
   • Muscle Gain: Calories = TDEE + 250-500 (for slow, lean gains)

Manual Calculation Example

Problem: Calculate maintenance calories and a weight loss target for a 30-year-old woman who is 165 cm tall, weighs 68 kg, and exercises 3 times a week (Moderately Active).

1. Calculate BMR (Female Formula): BMR = (10 × 68) + (6.25 × 165) - (5 × 30) - 161 BMR = 680 + 1031.25 - 150 - 161 BMR = 1400.25 calories
2. Determine Activity Multiplier: Moderately Active = 1.55
3. Calculate TDEE (Maintenance): TDEE = 1400.25 × 1.55 = 2170.39 calories
4. Calculate Weight Loss Target (500 calorie deficit): Target = 2170 - 500 = 1670 calories

Result: To lose weight, she should aim for approximately 1,670 calories per day.

How to Use the Online Calorie Calculator

Our online calorie calculator automates all these steps for quick and accurate results.

1. Enter Your Stats. Input your age, sex, weight, height, and activity level. The calculator handles unit conversions.
2. Select Your Goal. Choose from weight loss, maintenance, or muscle gain. You can often select the aggressiveness of the goal (e.g., mild or aggressive deficit).
3. Get Your Results. The calculator instantly displays your BMR, TDEE, and your recommended daily calorie target.
4. Review Macronutrients (Optional). Many calculators also provide a breakdown of protein, fat, and carbohydrate targets to optimise your diet.

Worked Examples

Example 1: Weight Loss for a Man

• Scenario: A 40-year-old man, 180 cm, 95 kg, Lightly Active. Goal: Lose weight.
• Calculation:
  1. BMR = (10×95) + (6.25×180) - (5×40) + 5 = 1,855 calories
  2. TDEE = 1,855 × 1.375 = 2,550 calories
  3. Weight Loss Target = 2,550 - 500 = 2,050 calories

Example 2: Maintenance for an Athlete

• Scenario: A 25-year-old female athlete, 170 cm, 65 kg, Very Active. Goal: Maintain weight.
• Calculation:
  1. BMR = (10×65) + (6.25×170) - (5×25) - 161 = 1,399 calories
  2. TDEE = 1,399 × 1.725 = 2,413 calories (her maintenance target)

Example 3: Muscle Gain

• Scenario: A 20-year-old man, 175 cm, 75 kg, Moderately Active. Goal: Build muscle.
• Calculation:
  1. BMR = (10×75) + (6.25×175) - (5×20) + 5 = 1,738 calories
  2. TDEE = 1,738 × 1.55 = 2,694 calories
  3. Muscle Gain Target = 2,694 + 300 = 2,994 calories

Practical Applications and Real-Life Uses

Calculating your calories helps you:

• Lose Fat Effectively: Create a controlled deficit to lose fat while preserving muscle.
• Build Muscle Efficiently: Ensure you're eating enough to support muscle growth.
• Break Plateaus: Understand why your weight has stalled and how to adjust your intake.
• Fuel Performance: Eat appropriately for your training volume as an athlete.

Pro Tips and Common Mistakes

• Pro Tip: Be honest about your activity level. Most people overestimate this. "Moderately Active" means genuine, heart-rate-raising exercise for 30-45 minutes, 3-5 times per week.
• Pro Tip: Use a food scale for 1-2 weeks. The most accurate calculation is useless if you underestimate your food intake. Weighing food teaches you what true portion sizes look like.
• Common Mistake: Creating too large a deficit. A deficit larger than 500-750 calories can lead to muscle loss, metabolic adaptation, and burnout. Slow and steady wins the race.
• Common Mistake: Not recalculating after weight loss. As you lose weight, your BMR decreases. Recalculate your needs every 5-10 kg of weight loss.

Frequently Asked Questions

How accurate is the Mifflin-St Jeor equation?

It is considered the most accurate BMR equation for the general population, with an accuracy of about ±10%. However, it is an estimate. Use the calculated number as a starting point and adjust based on your real-world results over 2-4 weeks.

Why am I not losing weight on a calorie deficit?

The most common reasons are: 1) Inaccurately tracking food intake (forgetting oils, sauces, drinks), 2) Overestimating your activity level, 3) Water weight fluctuations masking fat loss, or 4) An adaptive slowdown in metabolism. Re-check your calculations and tracking consistency before reducing calories further.

Should I include exercise calories in my calculation?

The activity multiplier you select already accounts for your exercise. Therefore, you should NOT add extra calories for workouts you've already factored in. If you use the "Sedentary" multiplier and then log exercise separately, some calculators may add those calories back, but this method is prone to overestimation.

Conclusion

Understanding how to calculate daily calories using your TDEE is a powerful skill that puts you in control of your nutrition. By applying the Mifflin-St Jeor equation and an appropriate activity multiplier, you can establish a scientific baseline for your diet. Remember, these numbers are a starting point. Monitor your progress and adjust as needed. For instant, accurate results, use our Calorie Calculator to find your personalised targets today.