Nutrition labels are designed by regulatory bodies and interpreted, often anxiously, by consumers. Most of the information on a label is either not relevant to most people's goals, or is presented in a way that requires context to be meaningful. Knowing what to look at first — and what to mostly ignore — makes the whole thing considerably less stressful.
Start with the serving size
Everything on a nutrition label is expressed per serving. The serving size is defined by the manufacturer and may bear no relationship to how much you'd actually eat. A serving of cereal might be 30g. A serving of pasta sauce might be 125g when the jar contains 500g and you'd use most of it on one meal.
Before reading any other numbers, check the serving size and mentally adjust everything else accordingly. Labels also often list nutritional information per 100g alongside the per-serving column — this is often the more useful comparison for evaluating foods against each other.
The three numbers worth paying attention to
Calories (kilojoules or kilocalories). This is the energy content. In the context of energy balance, this is the most useful number — though it's an estimate, not a precise measurement. The kilojoule figure is what Australian labels typically lead with. 4.2 kJ ≈ 1 kcal.
Protein. If you're tracking protein intake, this is the number to check. Expressed in grams per serving. High-protein foods are generally above 15–20g per serving.
Dietary fibre. A useful marker of food quality that correlates with satiety and gut health. Foods above 3–5g per serving are reasonable sources of fibre.
What you can largely ignore
Total fat as a standalone number is less useful than it appears — what matters is the type and source of fat, not the quantity alone.
Sugar on a label includes both added sugars and naturally occurring sugars (from fruit, dairy). A yoghurt and a soft drink can have similar sugar numbers for very different reasons. Added sugars are more relevant to track, but most Australian labels don't distinguish them clearly.
The % Daily Intake (%DI) column is based on a reference diet of 8,700 kJ per day. This may have nothing to do with your actual intake. Treat it as approximate context, not a target.
The ingredients list
The ingredients list tells you what's actually in the food, listed in descending order by weight. If the first two or three ingredients are whole foods (oats, almonds, water), you have a reasonable sense of what you're eating. If they're forms of sugar, refined starches, or ingredients you couldn't find in a kitchen, that's useful information too.
The ingredients list is often more informative than the nutrition panel for understanding food quality. The panel tells you the numbers; the list tells you what produced them.