How to calculate how much energy your body needs? A comprehensive nutrition diet guide

October 26, 2025 •

2 min read

According to the National Institutes of Health, the Mifflin-St Jeor equation is one of the most reliable methods for estimating resting metabolic rate. To build an effective nutrition diet, understanding how to calculate how much energy your body needs is the crucial first step. This knowledge is the foundation for managing your weight and achieving health goals, whether you aim to gain, lose, or maintain.

Quick Summary

This guide provides a detailed breakdown of how to calculate your body's energy requirements, covering the basal metabolic rate (BMR), total daily energy expenditure (TDEE), and the factors that influence these numbers. It explains the formulas and activity multipliers necessary to estimate your daily calorie needs for effective weight management.

Key Points

Start with BMR: Calculate your Basal Metabolic Rate (BMR) using the Mifflin-St Jeor equation, which estimates the calories your body burns at complete rest.
Factor in Activity: Multiply your BMR by an activity multiplier (1.2 to 1.9) to find your Total Daily Energy Expenditure (TDEE), accounting for all daily movement and exercise.
Adjust for Your Goal: Create a calorie deficit (fewer calories than TDEE) to lose weight or a calorie surplus (more calories than TDEE) to gain weight.
Understand Macronutrients: Be mindful of where your calories come from, focusing on a balanced intake of protein, carbohydrates, and fats, as each has a different caloric and metabolic impact.
Seek Professional Guidance: Predictive equations are estimates; for personalized advice, especially for weight loss or gain, consult a healthcare provider or registered dietitian.
Monitor and Adjust: Your energy needs will change as your weight or activity level changes. Recalculate your TDEE periodically to ensure your intake aligns with your goals.

Understanding your body's energy requirements is a fundamental aspect of creating an effective nutrition plan. Your total daily energy expenditure (TDEE) is a combination of three main factors: your basal metabolic rate (BMR), the thermic effect of food (TEF), and your physical activity level. By accurately estimating these components, you can personalize your diet for your unique needs.

Step 1: Calculating Your Basal Metabolic Rate (BMR)

Your BMR represents the number of calories your body needs to perform its most basic, life-sustaining functions while at rest. It's the largest part of your TDEE, accounting for 60–70% of daily energy use. The Mifflin-St Jeor equation is a widely used and accurate way to estimate your BMR.

For Men: $BMR = (10 \times \text{weight in kg}) + (6.25 \times \text{height in cm}) - (5 \times \text{age in years}) + 5$
For Women: $BMR = (10 \times \text{weight in kg}) + (6.25 \times \text{height in cm}) - (5 \times \text{age in years}) - 161$

Example BMR Calculation

For a 30-year-old woman, 165 cm tall, weighing 68 kg: $BMR = (10 \times 68) + (6.25 \times 165) - (5 \times 30) - 161 = 1400.25$ calories per day. BMR is influenced by genetics, muscle mass, and thyroid hormone levels.

Step 2: Incorporating Your Activity Level for TDEE

Your TDEE is your BMR adjusted for physical activity. Multiply your BMR by an activity multiplier based on your lifestyle:

Sedentary: BMR x 1.2
Lightly Active: BMR x 1.375
Moderately Active: BMR x 1.55
Very Active: BMR x 1.725
Extra Active: BMR x 1.9

Using the previous example (BMR 1400.25) for a moderately active woman: $TDEE = 1400.25 \times 1.55 = 2170.38$ calories per day. This estimates her daily maintenance calories, including the Thermic Effect of Food (TEF).

Step 3: Modifying Your Intake for Your Goal

Adjust your daily calorie intake based on your TDEE to meet your weight goals.

Weight Loss: Create a 500-1000 calorie deficit below TDEE for 0.5-1 kg loss per week. Do not eat below your BMR.
Weight Gain: Increase daily intake by 300-500 calories above TDEE, focusing on muscle gain.

TDEE Calculation: Mifflin-St Jeor vs. Harris-Benedict

The Mifflin-St Jeor equation is generally more accurate for modern lifestyles than the older Harris-Benedict formula.


Aspect	Mifflin-St Jeor Equation	Harris-Benedict Equation
Year Developed	1990	1919 (revised 1984)
Accuracy	More reliable	Less accurate, especially in obese individuals
Units Used	Metric	Imperial versions common

Macronutrients and Energy

Protein and carbohydrates provide 4 calories per gram, while fats provide 9 calories per gram. Macronutrient balance is crucial; a general guideline is 45-65% carbohydrates, 20-35% fat, and 10-35% protein. Higher protein (25-35%) can help with weight loss.

Conclusion

Calculating your BMR and TDEE using equations like Mifflin-St Jeor helps establish your energy needs. Adjusting intake based on your goals and balancing macronutrients supports sustainable progress. These are estimates; professional guidance is recommended for tailored results.

Finding More Resources

The National Institutes of Health (NIH) is a valuable resource for information on nutritional science and dietary guidelines.

Frequently Asked Questions

BMR (Basal Metabolic Rate) is the minimum energy your body needs to function at rest, while TDEE (Total Daily Energy Expenditure) is your BMR plus the energy you burn from all daily activities, including exercise and digestion.

The Mifflin-St Jeor equation is generally considered more accurate for estimating BMR in modern populations compared to the older Harris-Benedict equation.

For sustainable weight loss, a daily calorie deficit of 500-1000 calories below your TDEE is often recommended. This typically results in a weight loss of 0.5-1 kg per week.

No, it is not recommended to eat below your BMR. Your BMR represents the energy your body needs to perform essential functions, and eating less than this can negatively impact your health and metabolism.

TEF is the energy your body uses to digest, absorb, and metabolize the food you eat. It typically accounts for about 10% of your total daily energy expenditure.

Muscle tissue requires more energy to maintain than fat tissue. Therefore, individuals with higher muscle mass generally have a higher BMR and higher overall energy needs.

Yes, it is important to recalculate your TDEE periodically, such as every 5-10 kg of weight loss, as a lighter body requires less energy to function and move.