Portion Calculator

Match the hand to the child, always. For most school-age children, a cupped handful equals roughly a serving of the fruit or vegetable group, a fist equals a serving of the grain or starch group, a palm equals a serving of the protein group, and a thumb equals a serving of fats, spreads and oils. The guide is most reliable for children roughly between the ages of four and twelve, because the hand-to-body ratio is stable in that range. For a teenager, the hand guide underestimates, so go back to the cup and ounce table. The key point is that these are approximate equivalents, not precision instruments: if your child eats noticeably less or more than the guide suggests, trust the observation over the guide, and adjust the portion rather than the rule.

Because age is a poor proxy for need. Two ten-year-olds can differ substantially in body size, growth pattern, and how much energy they burn on a given day, and the standard guidance only offers age bands because it has to cover the whole band. Some children also eat differently at different times: a child who is genuinely hungry in the morning and not at lunch needs a different shape of lunch from one who is the opposite. There is no single correct portion, and that is why this tool gives you a range and a starting point rather than a rule. Watch out for the two failure modes at either end: packing well beyond the target because it feels wasteful to leave food behind, which trains the child to waste food, and packing too little so that the child buys more at school or eats badly at dinner. The honest measure of a correct portion is what comes back in the lunchbox.

Here are the easy-to-get-wrong inputs. First, using an outdated weight. Second, entering high activity for a single practice day and then packing that lunch every day. Third, reading the lunch figure as an exact target that must be hit, when it is a starting point to adjust. Fourth, using your own hand in the visual guide instead of the hand of the child. Fifth, packing the same volume every single day regardless of how the previous day went. Sixth, ignoring the food group balance entirely and simply scaling up the amount of whatever the child already likes. A common mistake worth naming is measuring the lunch at home in cups and then packing it into a larger container, because a fuller container looks like more food to a child than the same food in a smaller one. The key point is to adjust portion by observation over time, not by calculation alone.

The scope is general portion guidance for school-age children using standard average formulas. It is an estimate, and it will not be exact for any individual child. It is not medical nutrition therapy, and it is not suitable as the plan for a child with a diagnosed condition such as diabetes, coeliac disease, a food allergy, a growth disorder or a condition requiring a prescribed diet; those plans belong with a pediatrician or a registered dietitian, and no calculator should override them. This page gives no medical advice and no information about medicines or doses. For allergies, use a read-the-label self-check for every product that goes into the box, and follow the rules published by your school and your local authority about what may be packed, since those rules take priority over any number here. The hand guide also has clear limits: it is a rough visual aid for younger children, it breaks down for teenagers and for children with limited hand function, and it tells you nothing about whether the food itself is suitable. When the calculation and the observation disagree, the observation wins. When the calculation and a health professional disagree, the professional wins.