Kilojoule Deficit Calculator
A kilojoule deficit is the difference between what you eat and what your body needs. This calculator shows your deficit and translates it into predicted weekly weight loss.
Related tools
Enter your details
Your Energy Balance
ExampleExample figures, not your own. Worked for a moderately active 40 year old woman of 80 kg and 168 cm eating 7,500 kJ a day. Enter your own details and press Calculate.
Daily Deficit
2,452kJ/day
You are in a calorie deficitPredicted Weekly Weight Loss
0.53kg/week
Maintenance Level
9,952kJ/day
How It Works
Your deficit = maintenance kJ - daily intake kJ. One kilogram of body fat stores approximately 32,200 kJ. Your weekly deficit divided by 32,200 gives the predicted weekly weight loss in kg.
How to use it
- 1Enter your gender, age, weight, height, and activity level to calculate maintenance kJ
- 2Enter your current daily kJ intake (or target)
- 3Click "Calculate" to see your deficit and predicted weekly weight loss
Quick Reference
| Daily Deficit (kJ) | Weekly Loss (kg) | Monthly Loss (kg) |
|---|---|---|
| 1,150 | 0.25 | ~1.0 |
| 2,300 | 0.50 | ~2.0 |
| 3,450 | 0.75 | ~3.0 |
| 4,600 | 1.00 | ~4.0 |
Assumes consistent deficit. Actual results vary with metabolic adaptation.
How This Is Calculated
- maintenance kJ
- = your TDEE (BMR × activity multiplier)
- daily intake kJ
- = the kilojoules you eat per day
- 32,217
- = kJ stored in 1 kg of body fat
A safe deficit is 2,000–3,000 kJ (500–750 kcal) per day, resulting in weight loss of 0.5–0.75 kg per week. Larger deficits can lead to muscle loss.