School Meal Portion Calculator
This school meal portion calculator turns cafeteria portion weights into total quantities to prep: headcount by age group, edible yield and an optional reserve. School lunch quantities come out per group and overall, with multiple daily services supported.
One group = guests sharing the same portion weight
Calculated results
Portion weights must come from a menu and a reference framework suited to your diners: this calculator determines no regulatory or medical nutritional requirement.
Mode: portion weight applied at each service
Method and limits
How to use this calculator
Pick the number of groups — a group is students sharing the same portion weight — then enter each group's name, its headcount and its net portion weight in grams. Enter the overall edible yield of the preparation, the optional reserve and the number of daily services, stating whether the portion applies at each service or totals the full day. Net, raw and purchase quantities appear instantly, per group and overall.
In per-service mode, the net quantity is Q_net = Σ(N_g × P_g) × S / 1000, where N_g is the group's headcount, P_g its portion weight in grams and S the number of services; in total mode, the multiplication by S disappears. The raw quantity follows Q_raw = Q_net / (Y/100), then the reserve applies once: Q_buy = Q_raw × (1 + r/100). Portion weights must come from a menu and a reference framework suited to your diners.
From grams per student to kilograms of prep
One hundred students served 150 g (about 5.3 oz) each need 15 kg (33.1 lb) net; two services double the requirement to 30 kg in per-service mode, while in total mode the entered portion already covers all services. The raw quantity follows Q_raw = Q_net / (Y/100) — at 90% edible yield, 15 kg net requires 16.67 kg (36.7 lb) raw — and the reserve r applies once: Q_buy = Q_raw × (1 + r/100), i.e. 18.33 kg (40.4 lb) with 10%. Portion, then yield, then reserve: exactly the order school kitchen math runs in, with no double counting.
Groups, validation and limits
Each group needs a name, a strictly positive headcount and a valid portion weight: an incomplete line blocks the calculation rather than guessing values. Zero yield is rejected, the reserve is capped at 30% with a confirmation requested above 20%, and services range from 1 to 3. The calculator never infers children's nutritional needs from age: it turns decided portion weights — those of your school meal reference framework — into a procurement list, nothing more.
Worked example
One hundred students at 150 g net each, a 90% edible yield, one service and no reserve: net quantity to serve 15 kg (33.1 lb), raw quantity to prep 16.67 kg (36.7 lb) and quantity to purchase 16.67 kg. A 10% reserve raises purchases to 18.33 kg (40.4 lb); in per-service mode, two services double the net requirement to 30 kg (66.1 lb). Reproduce these values in the tool: you must get exactly the same results.
Assumptions and limits
Portion weights come from your menu and a reference framework suited to your diners: the calculator determines no regulatory or medical nutritional requirement, and refuses to infer a portion from age. The edible yield is global to the preparation; service losses — plate waste, day-to-day variation — are handled through the reserve, capped at 30% and confirmed above 20%. The reserve applies once, on the raw quantity; per-service mode multiplies quantities by the number of services, total mode does not.
Frequently asked questions
Limits of use