What is the formula for calories?

December 28, 2025 •

2 min read

The average person needs roughly 2,000 calories daily. However, an individual's actual calorie requirements vary. The formula for calories combines Basal Metabolic Rate (BMR) with activity level.

Quick Summary

This guide breaks down calorie formulas. It explains how to determine your Basal Metabolic Rate (BMR) and Total Daily Energy Expenditure (TDEE) using the Mifflin-St Jeor and Harris-Benedict equations. Learn the factors affecting your calorie needs for weight management.

Key Points

Formula Involves BMR and Activity: Calculate calorie needs by determining your Basal Metabolic Rate (BMR) and adjusting for activity level.
Mifflin-St Jeor Equation: This equation uses weight, height, age, and gender.
Harris-Benedict Equation: An older method that also uses weight, height, age, and gender to estimate BMR.
Katch-McArdle Equation: Uses lean body mass and is most accurate for those with a low body fat percentage.
Activity Level is Key: TDEE is determined by multiplying BMR by an activity factor.
Calorie Balance for Weight Control: Weight loss requires a calorie deficit; weight gain requires a surplus.
Macronutrient Calories: Carbohydrates and protein provide 4 kcal/g, while fat provides 9 kcal/g.

Understanding the Calorie Formula

There isn't a single formula that applies universally when calculating daily calorie needs. You must first estimate your Basal Metabolic Rate (BMR) and adjust for your physical activity. BMR is the energy your body uses at rest for basic functions. Total Daily Energy Expenditure (TDEE) accounts for calories burned through daily activities.

Various equations estimate BMR. These include the Mifflin-St Jeor equation, the revised Harris-Benedict equation, and the Katch-McArdle formula.

Common BMR Equations

Mifflin-St Jeor Equation

This equation is often preferred for accuracy. It utilizes weight, height, age, and gender.

Revised Harris-Benedict Equation

This is a classic method revised for improved accuracy. It uses weight, height, age, and gender.

Katch-McArdle Formula

This formula is unisex and uses lean body mass (LBM) to estimate Resting Metabolic Rate (RMR). It requires knowing your body fat percentage, which makes it more accurate for athletic individuals.

Calculating Total Daily Energy Expenditure (TDEE)

To find your TDEE, multiply your BMR (or RMR) by an activity factor that reflects your daily activity. Activity multipliers range from 1.2 (sedentary) to 1.9 (extra active).

Comparing Calorie Formula Equations


Feature	Mifflin-St Jeor	Revised Harris-Benedict	Katch-McArdle
Primary Metric	Basal Metabolic Rate (BMR)	Basal Metabolic Rate (BMR)	Resting Metabolic Rate (RMR)
Input Variables	Weight, Height, Age, Gender	Weight, Height, Age, Gender	Lean Body Mass (LBM)
Accuracy	Most accurate for general population	Still widely used	Most accurate for athletes
Complexity	Simple	Simple	More complex, requires body fat %
Best Used For	Most people	Broad range of individuals	Individuals with body composition data

Using the Calorie Formula for Weight Management

Your TDEE represents your maintenance calorie level. Consume less than your TDEE to lose weight, more to gain weight, and an equal amount for maintenance. A deficit of 500 calories daily can lead to approximately one pound of weight loss weekly.

Macronutrients

Macronutrients provide different calorie amounts: carbohydrates and protein have 4 calories per gram; fat has 9 calories per gram.

Conclusion

Calculating calorie needs involves using a BMR equation (Mifflin-St Jeor or Revised Harris-Benedict) and applying an activity factor to find your TDEE. The Katch-McArdle formula is useful if you have body composition data. These equations provide estimates; consult a professional for personalized guidance.

Frequently Asked Questions

For a general estimate, multiply your body weight in pounds by 15. This is a rough estimate for moderately active individuals.

BMR is calories burned at rest, and TDEE is BMR adjusted for physical activity.

Calculate your TDEE and consume fewer calories. A 500-1000 calorie deficit is often suggested for 1-2 pounds of weight loss per week.

Mifflin-St Jeor is often considered most accurate for the general population, whereas Katch-McArdle is better for athletes.

Protein and carbs provide 4 calories per gram, fat provides 9 calories per gram.

No, excessively low intake can be harmful. Avoid dropping below 1,200 calories (women) or 1,500 calories (men) without medical advice.

Activity level significantly impacts TDEE. BMR is multiplied by an activity factor (1.2 to 1.9) based on exercise.