Free calculator

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

Your Daily Energy Needs

Example

Example figures, not your own. Worked for a moderately active 30 year old woman of 70 kg and 165 cm. Enter your own details and press Calculate.

Total Daily Energy Expenditure

9,573kJ/day

Estimated energy to maintain your current weight

Basal Metabolic Rate (BMR)

6,176kJ/day

Energy your body needs at complete rest

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.

How to use it

1Select your gender
2Enter your age in years
3Enter your weight in kilograms
4Enter your height in centimetres
5Select your activity level
6Click "Calculate" to see your daily energy needs in kilojoules

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.

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.

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.

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