Quick answer
Look for the Energy row. It may show kJ, kcal or both, once per serving and once per 100 g (or 100 mL). If only kJ is shown, divide by 4.184 for kcal. If only kcal is shown, multiply by 4.184 for kJ.
Step 1: Find the energy row
On an Australian or New Zealand Nutrition Information Panel, energy is the first row, in kJ. On EU and UK labels, you will usually see both, for example "1046 kJ / 250 kcal". US labels show Calories in large type near the top.
Step 2: Check whether the numbers are per serving or per 100 g
Most panels have two columns. The per-serving column tells you what you eat if you eat the stated serving. The per-100 g column is for comparing products fairly, because it removes serving-size differences.
To change per 100 g into per serving, use this formula: energy per serving = energy per 100 g × serving size in g ÷ 100.
Example: A cereal shows 1,500 kJ per 100 g and a 30 g serving. The serving is 1,500 × 30 ÷ 100 = 450 kJ, which is 107.55 kcal.
Step 3: Compare kJ and kcal on the same label
If both units are printed, the ratio is usually close to 4.184. A label reading 1046 kJ and 250 kcal fits exactly (1,046 kJ = 250 kcal). Small gaps are normal because manufacturers calculate and round each unit separately using standard energy factors (see our methodology).
Step 4: Use the % daily intake wisely
Australian and New Zealand labels show a percentage based on an 8,700 kJ day. For the cereal above, 450 kJ is 5.2% of 8,700 kJ. Remember that the reference is an average, not your personal target. See how many kJ you should eat per day.
Step 5: Count servings per pack
A bottle or packet often contains more than one serving. Multiply the per-serving energy by the number of servings you actually eat. A 2-serve pack at 1,046 kJ per serve is 2,092 kJ (500 kcal) if you finish it.
Common traps
- "As sold" vs "as prepared." Powdered products and dry pasta may show energy for the dry weight.
- Serving size differences. Two brands with the same serving energy may use different serving sizes.
- Unit mix-ups. 500 kJ is not 500 calories. It is 119.5 kcal. Use the KJ to Cal converter when in doubt.
Frequently asked questions
Which is better on a label, kJ or kcal?
Neither. They are the same energy in different units. Use the one you track, and convert with kcal = kJ ÷ 4.184.
Why do kJ and kcal on my label not match exactly?
Labels calculate each unit from rounded energy factors and round again, so a small mismatch can appear.
Should I use per serving or per 100 g?
Use per serving for what you will eat, and per 100 g to compare products.
Last updated 11 Oct 2026. How we calculate.