How many calories are in cornflakes?
Plain cornflakes are about 380 kcal per 100 g, so the box’s 30 g serving is roughly 110 kcal. A real bowl is rarely 30 g, and with milk the total is usually 280 to 330. Two gaps open between the label and the breakfast, and both run the same way.
Per portion
| Portion | Calories | Protein | Carbs | Fat |
|---|---|---|---|---|
| 30 g, the box’s own serving | ~110 kcal | 2 g | 25 g | 0.2 g |
| 50 g, a modest bowl | ~190 kcal | 3.5 g | 42 g | 0.4 g |
| 70 g, a filled bowl | ~265 kcal | 5 g | 59 g | 0.6 g |
| 100 g plain cornflakes | ~380 kcal | 7 g | 84 g | 0.9 g |
| 50 g flakes + 200 ml whole milk | ~320 kcal | 10 g | 52 g | 7.5 g |
| 50 g flakes + 200 ml skimmed | ~260 kcal | 10 g | 52 g | 0.8 g |
| 50 g flakes, whole milk, 2 tsp sugar | ~350 kcal | 10 g | 60 g | 7.5 g |
What changes the number
The milk, more than the cereal. 200 ml of whole milk is about 130 kcal against 190 for 50 g of flakes, and most people pour nearer 250 ml, which is 160 — more than the cereal underneath. Whole to skimmed saves 60 kcal and costs no protein. Unsweetened almond drink is 30 kcal per 200 ml; sweetened soya and oat, 90 to 140.
What you weigh versus what you pour. Cornflakes are light and bulky: 30 g is about one level cup and looks mean in an adult bowl. Weigh your pour once; most people find 50–70 g, nearly twice the labelled serving.
Sugar on top. Two teaspoons is 32 kcal, a sliced banana 90–100, honey 60. Frosted flakes carry roughly 35 g of sugar per 100 g against 8 g for plain, but barely more energy: sugar and starch cost the same per gram.
Fat is not the variable. Plain flakes are under 1 g of fat per 100 g. Everything fatty in this bowl arrives from the jug.
Where it fits in a deficit
Cornflakes are an efficient way to eat 300 kcal without noticing. At 380 kcal per 100 g the dry flakes sit high on the calorie-density ladder, with 2 g of protein and under 1 g of fibre a serving; the milk carries almost all the protein in the bowl.
The honest version is that most people are hungry by eleven. The cheap fixes are weighing the flakes, going down a milk grade, and adding protein — a 150 g pot of 0% Greek yoghurt in place of some of the milk adds 90 kcal and 15 g, and a scoop of protein powder stirred in adds about 120 kcal and 24 g. Against a day’s calorie deficit, a 260 kcal bowl that fails at eleven is worse value than a 350 kcal one that holds.
“Fortified” and “no added sugar”, honestly
Both are true, and neither means what it is read to mean.
Fortified means vitamins and iron were added during manufacture. That is real: fortified cereal is a genuine source of iron, folate and B vitamins. It says nothing about calories or how filling the bowl is, and a fortified frosted flake is still mostly starch and sugar.
No added sugar describes what the manufacturer put in, not what is in your bowl. Plain cornflakes already carry about 8 g of sugar per 100 g, and the honey or banana you add is sugar.
And the % reference intake column assumes a 2,000 kcal day, which may be nothing like your maintenance level. As with a packet of Maggi, the per-serving column answers a question about a portion you did not choose. The per-100 g column is the one that compares.
Figures are typical values and vary by variety, size and preparation. General information, not medical advice.