Quick answer
Food labels use 8,700 kJ (about 2,079.35 kcal) as an average adult reference day in Australia and New Zealand. Your own needs depend on age, sex, size and activity, and many adults fall somewhere between roughly 7,000 and 12,000 kJ a day. Treat every figure here as an estimate.
Reference intakes on food labels
| Region | Label basis | kJ | kcal |
|---|---|---|---|
| Australia and New Zealand | 8,700 kJ average adult diet | 8,700 kJ | 2,079.35 kcal |
| European Union | Reference intake of an average adult (8,400 kJ / 2,000 kcal) | 8,400 kJ | 2,000 kcal |
| United States | Daily Value based on 2,000 calories | 8,368 kJ | 2,000 kcal |
These numbers exist so labels can show "% of daily intake" for one typical adult. They are not targets for you. The EU rounds 2,000 kcal to 8,400 kJ, which is why it differs slightly from the exact 8,368 kJ.
What decides how much energy you need?
- Age and sex. Energy needs generally fall with age and are higher on average for men.
- Body size. Larger bodies use more energy at rest.
- Activity. A desk job and a building site can differ by thousands of kJ a day.
- Life stage and health. Pregnancy, breastfeeding, growth in teenagers and medical conditions all change needs.
How to estimate your own daily energy in kJ
A common method has two steps. First, estimate the energy you burn at rest, called basal metabolic rate (BMR), with the Mifflin–St Jeor equation, which uses weight in kg, height in cm and age in years:
- Men: BMR (kcal) = 10 × weight + 6.25 × height − 5 × age + 5
- Women: BMR (kcal) = 10 × weight + 6.25 × height − 5 × age − 161
Second, multiply by an activity factor:
| Activity level | Factor |
|---|---|
| Sedentary (little exercise) | 1.2 |
| Lightly active (1–3 days a week) | 1.375 |
| Moderately active (3–5 days a week) | 1.55 |
| Very active (6–7 days a week) | 1.725 |
| Extra active (hard training or physical job) | 1.9 |
Finally, multiply kcal by 4.184 to get kJ.
Worked examples
| Person | BMR | Activity | Daily energy |
|---|---|---|---|
| Woman, 30 years, 165 cm, 65 kg | 1,370 kcal (5,733 kJ) | Lightly active (1.375) | 1,884 kcal (7,883 kJ) |
| Man, 35 years, 178 cm, 80 kg | 1,743 kcal (7,291 kJ) | Moderately active (1.55) | 2,701 kcal (11,300 kJ) |
You can run your own numbers in the daily energy calculator, which shows the result in kJ and kcal.
Important limits
Equations like this are estimates, and real needs can differ by 10% or more. They are meant for healthy adults. They are not suitable for children, pregnancy, or people with medical conditions. If you want to change your weight, or you have a health condition, speak to your doctor or an accredited dietitian before changing how much you eat.
Counting in kJ or kcal
Use the unit that matches your labels. In Australia and New Zealand that means kJ. If a plan is written in kcal, convert it once with the calories to kJ converter: for example, 2,000 kcal is 8,368 kJ.
Frequently asked questions
Is 8,700 kJ a day enough?
8,700 kJ is only a label reference for an average adult. Some people need more and some need less. Use the daily energy calculator for a personal estimate.
How many kJ is 2,000 calories?
2,000 kcal is 8,368 kJ.
How many kJ do I burn at rest?
It varies with your size, age and sex. The Mifflin–St Jeor equation on this page gives a typical estimate of resting energy use.
Last updated 11 Oct 2026. How we calculate.