Did you know? Two packets can both say “6 grams of sugar” and still contain very different amounts of sugar for the portion your child actually eats. The number is not wrong. The missing question is: six grams per what?
The useful answer: per serving describes the amount in one stated serving, serving size tells you how big that serving is, servings per package tells you how many of those portions the pack contains, and per 100g gives a common weight for comparing similar foods. Learning these phrases helps families make fairer comparisons rather than being fooled by different portions.
One label, four different questions
A Primary 5 student called Hana brings home a worksheet on nutrition labels. The family has a packet of crackers on the table. A label might say “Serving size: 30g”, “Servings per pack: 4”, “Sugar: 6g per serving” and “Sugar: 20g per 100g”. These are hypothetical teaching figures, not results from a tested brand or a real student. The four lines answer different questions, so none should be read alone.
Serving size is the reference portion used for calculations on that product’s label. A serving might be 30g, half a cup, one biscuit, or another defined amount. The stated serving is not a command to eat precisely that quantity, nor a guarantee that every family would choose it. Servings per package says how many such reference portions the container holds. In our example, four times 30g is 120g.
Per serving means “for one of these portions”. If Hana eats two of the stated 30g servings, she has eaten 60g. For the listed sugar value she would calculate 2 × 6g = 12g. Per 100g is a standard comparison base: 6g sugar ÷ 30g food × 100g = 20g sugar per 100g food. The same nutrient is being described from a different denominator.
Why the word “per” is the most important word on the panel
In Mathematics, per signals a rate or ratio. “Six grams per serving” is not the same statement as “six grams per packet”. It resembles other useful phrases: 60 kilometres per hour, 4 dollars per kilogram, or 12 pages per day. The denominator tells us the unit against which the number makes sense. Remove that unit and even an accurate number becomes misleading.
This is also a reading comprehension skill. The small words per, of, each, total and approximately often do more work than the large, bold words on the front of a packet. A student who reads “each 30g serving contains 6g” carefully is preparing for a broader habit: never detach a statistic from the quantity it refers to.
Worked comparison: which cereal has less sugar?
Imagine two entirely fictional cereals. Cereal A declares 6g sugar per 30g serving. Cereal B declares 4g sugar per 25g serving. If Hana compares only 6 and 4, she will immediately pick B, but she has not yet made a fair comparison. The serving weights differ.
Convert A to the same base: (6 ÷ 30) × 100 = 20g sugar per 100g. Convert B: (4 ÷ 25) × 100 = 16g sugar per 100g. B is indeed lower per equal weight, but now we know why. Had the numbers been closer or the servings more uneven, guessing from “per serving” alone could have produced the opposite decision.
If the actual breakfast bowl contains 50g, estimate the sugar from these hypothetical labels: A gives (20 ÷ 100) × 50 = 10g; B gives (16 ÷ 100) × 50 = 8g. This calculation describes one nutrient only. A complete food decision can also involve fibre, sodium, energy, other nutrients, allergies, the rest of the meal and personal needs.
The word families and label phrases worth teaching
Portion is an amount someone chooses or is served; serving is the amount a label or recipe defines. They sometimes coincide, but they are not interchangeable. Net weight usually refers to food content excluding its packaging, whereas drained weight concerns certain foods sold with liquid. The distinction is explained separately in eduKate’s guide to net and drained weight.
Nutrient and nutrition are related but not synonyms: nutrients are substances such as protein or sodium; nutrition is the broader subject of how food supports the body. Energy on a food label may be stated in kilocalories (kcal) or kilojoules (kJ); sodium and salt are connected but not numerically identical label terms. When comparing labels, read the named nutrient and its unit together.
Useful sentence frames include: “This contains 8g per 100g,” “The label defines one serving as 25g,” and “Our bowl is twice the labelled serving.” Those sentences have a precision that “This one is healthier because the number is smaller” lacks.
Three mistakes that can survive a correct calculation
Mistake one: comparing different denominators. One packet says 5g per serving and another says 14g per 100g. We cannot choose the lower concentration until we know the first packet’s serving mass. The repair is to normalise both values to the same denominator, preferably per 100g for similar solid foods.
Mistake two: assuming the whole packet equals one serving. A packet marked “4 servings” may be eaten across several days—or all at once—but the nutrient total changes with the amount consumed. If a pack has four identical servings, the whole-pack amount is four times the per-serving amount, subject to rounding of printed values.
Mistake three: treating a single nutrient as a full verdict. A product with less sugar per 100g is not automatically better in every relevant way. Read the context: ingredients, other panel values, energy, special dietary requirements and actual portion. Separate what the numbers prove from the larger judgement they might inform.
A five-minute supermarket practice for parents and students
Choose two comparable packaged foods—not an energy drink versus a breakfast cereal. Ask the child to locate serving size, servings per pack, per serving and per 100g. Let them point to the denominator before reading the amount. Then cover the per-100g column, invite them to calculate it, and reveal the printed value to discuss any rounding.
Next, vary the task. “What if I eat half the pack?” “What if two children share three servings?” “Which food has less sodium for the same 100g?” These are fresh retrieval and application questions, not a request to recite label definitions. A tutor can use exactly the same method to connect English vocabulary, ratios and unit conversion in a small-group learning activity.
For Secondary G1/G2/G3 learners, the next step is to explain a comparison in a sentence, not merely produce an answer. For example: “B contains four fewer grams of sugar than A per 100g of product.” This is a controlled, practical example of data interpretation; it does not claim a particular examination question or guarantee a grade.
A quick diagnostic: is the student reading the unit?
Ask: (1) Can you identify the unit after per? (2) Does a 45g bowl equal the stated 30g serving? (3) Are you comparing like with like? (4) If 4 servings are listed, do you know whether the pack total has been calculated? (5) Can you name one thing that the sugar figure cannot tell you by itself?
If a child gets the arithmetic right but cannot explain “per”, practise the language first. If they can define the words but multiply by the wrong number of servings, practise a single three-line calculation. If they conclude that the lowest sugar value settles every food decision, practise the evidence boundary. Small repairs are often more useful than another large list of food words.
Frequently asked questions
Does “per 100g” mean I should eat 100g?
No. It is a comparison unit, not a recommendation about how much anyone should eat. The actual amount consumed and individual needs remain separate questions.
Why can two brands use different serving sizes?
Serving size is stated for a product and can vary between products. That is why a fair same-weight comparison usually uses values per 100g for solids, or per 100ml for liquids, where those figures are available.
Can I multiply the per-serving figure by the servings in the pack?
Yes, to estimate the whole-pack amount when the servings are consistently defined. Remember that label values may be rounded, and confirm whether the pack truly contains the stated number of servings.
Is the nutrition information panel enough to check allergies?
No. Read the ingredients and relevant allergen information separately. A nutrient table alone does not establish whether a food is suitable for someone with an allergy.
Reliable sources and one useful next step
Singapore’s Health Promotion Board explains the Nutrition Information Panel, while HealthHub explains serving size and fair per-100g comparisons. These official resources support the terminology used here. To explore another easily confused label claim, see sugar-free, no added sugar and unsweetened.
Takeaway: Teaching vocabulary does not end when a student knows the dictionary definition of serving. The real success is when they can read the denominator, calculate fairly, explain a choice, and recognise what the numbers have not proved. That is a life skill carried by a few precise words.