Basal Metabolic Rate (BMR) is the number of kilojoules your body needs to maintain basic functions at rest - breathing, circulation, cell production. It typically accounts for 60-75% of total daily energy expenditure.

How many kJ per day for a woman?

The average Australian woman needs approximately 7,500-8,500 kJ per day, depending on age, weight, height, and activity level. Sedentary women may need less, while very active women may need 10,000+ kJ.

How many kJ per day for a man?

The average Australian man needs approximately 9,000-10,500 kJ per day. Active men or those with physical jobs may need 12,000+ kJ per day.

How accurate is the Harris-Benedict formula?

The Harris-Benedict formula is accurate to within about 10% for most people. It may overestimate needs for overweight individuals and underestimate for very muscular people. It provides a good starting point for energy planning.

Daily Energy Needs Calculator

This calculator estimates your daily energy needs in kilojoules using the Harris-Benedict formula. It calculates your Basal Metabolic Rate (BMR) - the energy your body needs at rest - then adjusts for your activity level to give your Total Daily Energy Expenditure (TDEE).

Enter Your Details

Gender

Age

years

Weight

Height

Activity Level

How It Works

The Harris-Benedict formula calculates BMR based on gender, weight, height, and age. For men: BMR = 88.362 + (13.397 × weight) + (4.799 × height) - (5.677 × age). For women: BMR = 447.593 + (9.247 × weight) + (3.098 × height) - (4.330 × age). The BMR is then multiplied by an activity factor (1.2 to 1.9) to get TDEE.

Quick Reference

Activity Level	Multiplier	kJ/day	kcal/day
Sedentary	×1.20	9,088	2,172
Lightly Active	×1.375	10,416	2,490
Moderately Active	×1.55	11,738	2,806
Active	×1.725	13,063	3,122
Very Active	×1.90	14,390	3,440

Example: 80 kg male, 175 cm, age 35.

Frequently Asked Questions

What is BMR?: Basal Metabolic Rate (BMR) is the number of kilojoules your body needs to maintain basic functions at rest - breathing, circulation, cell production. It typically accounts for 60-75% of total daily energy expenditure.
How many kJ per day for a woman?: The average Australian woman needs approximately 7,500-8,500 kJ per day, depending on age, weight, height, and activity level. Sedentary women may need less, while very active women may need 10,000+ kJ.
How many kJ per day for a man?: The average Australian man needs approximately 9,000-10,500 kJ per day. Active men or those with physical jobs may need 12,000+ kJ per day.
How accurate is the Harris-Benedict formula?: The Harris-Benedict formula is accurate to within about 10% for most people. It may overestimate needs for overweight individuals and underestimate for very muscular people. It provides a good starting point for energy planning.

How This Is Calculated

Male BMR (kcal) = 88.362 + (13.397 × weight) + (4.799 × height) − (5.677 × age) Female BMR (kcal) = 447.593 + (9.247 × weight) + (3.098 × height) − (4.330 × age) TDEE (kJ) = BMR × activity multiplier × 4.184

BMR: = Basal Metabolic Rate (energy at complete rest)
TDEE: = Total Daily Energy Expenditure
Activity multiplier: = 1.2 (sedentary) to 1.9 (very active)

Uses the revised Harris-Benedict equation (Roza & Shizgal, 1984). The activity multiplier accounts for exercise and daily movement.

Related Tools

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kJ Per Day to Lose Weight Calculator

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Disclaimer

This calculator provides estimates for informational purposes only and should not be considered medical advice. Individual results may vary based on factors not captured by these formulas. Consult a healthcare professional before making changes to your diet or exercise routine, especially if you have any existing health conditions.