In this article
A purchase starts from the service, the approved menu and the gross quantities in the recipe sheets, not from the supplier's item list. With these records linked, the team can explain why each ingredient is on the request and which quantity went into the calculation.
The calculation also keeps physical balance, reservations, orders not yet received and safety stock apart. If these figures are added together without a rule, the purchase can end up short, too large, or impossible to check afterwards.
The logic of the calculation
Direct answer
Calculate the gross ingredients the menu requires and add up each ingredient. Subtract only the available stock and the confirmed deliveries. Add the safety level the operation has defined and convert the result into packages to buy.
The recipe sheet links a preparation to its ingredients, its yield and the quantity per portion. The menu says which preparations will be used in each service. Demand says how many portions must be served. These three elements make up the gross need.
The final purchase quantity is different from the gross need. Before the request, the team must subtract what can be used, count deliveries that are firmly committed, and respect limits on packaging, shelf life, storage capacity and supplier lead time.
What data must be ready
For the calculation to give the same result every time, the records must be consistent. The ingredient needs a base unit, the recipe sheet must say whether the quantity is net or gross, and the yield must make sense for the portion in use. Demand must have a date, a service and a Unit.
In stock, quantities that are blocked, expired, reserved or in quarantine must not appear as available. An open order is also not the same as a confirmed delivery. This difference must be visible to whoever reviews the suggestion.
Swipe the table to see all the columns.
| Data | What it is for | Watch out for |
|---|---|---|
| Approved menu | Defines preparations, dates and services | Do not use a draft as confirmed demand |
| Valid recipe sheet | Gives the ingredient and the quantity per portion | Do not apply the correction factor twice |
| Target quantity | Sizes the portions for the service | Keep the forecast separate from the confirmed order |
| Available stock | Reduces what has to be bought | Exclude reservations and items that cannot be used |
| Confirmed deliveries | Reduce the need that is still open | An unconfirmed order is not stock |
| Purchase package | Converts the need into units that can be bought | Assess surplus, shelf life and storage |
Formulas for calculating the purchase
When the recipe sheet holds the net quantity, the correction factor can convert it into the gross quantity needed. If the sheet already holds the gross weight, the factor must not be applied again. The definition has to be the same in every recipe sheet used in the consolidation.
Safety stock should not be a generic percentage applied to every item. It can vary with consumption, replenishment lead time, predictability, perishability and company policy. If no policy has been defined, it is better to show zero and ask for a decision than to hide an arbitrary margin in the calculation.
Correction factor = gross weight / net weight
Gross need = sum(gross quantity per portion × portions)
Available stock = usable balance - reservations
Purchase need = maximum(0, gross need + safety - available stock - confirmed deliveries)
Packages = round up(purchase need / package content)Step-by-step procedure
The date of the calculation depends on the purchasing calendar and supplier lead times. Use demand and stock data with a known date and time. If demand changes, the team needs to know whether to recalculate everything, create a supplementary request or record the difference for the next cycle.
- Select the Unit, the period, the services and the approved version of the menu.
- Confirm the target quantity for each service and the share of each preparation when there are options.
- Expand the recipe sheets and convert ingredients to their base units.
- Add up the same ingredient across preparations, days and services in the calculated period.
- Check usable balance, reservations, open orders and confirmed deliveries.
- Apply the safety policy identified for the item and the period.
- Convert the net need into purchase packages and record the rounding.
- Review shelf life, storage capacity, minimum lot, lead time and substitutions before requesting.
Numerical example with rice
A Unit plans 500 meals. The recipe sheet uses 60 grams of raw rice per meal. The gross need is 30 kilograms. There are 10 kilograms in the balance, but 2 are reserved for another service. Available stock is therefore 8 kilograms. One delivery of 10 kilograms is confirmed and, in this example, the safety policy for the period is zero.
The purchase need is 12 kilograms. The supplier sells 5-kilogram packages, so the request needs three packages, 15 kilograms in total. The extra 3 kilograms are an explicit result of the packaging, not a hidden error. Before approving, the team checks whether the surplus can be stored and used within its shelf life.
500 meals × 60 g = 30 kg gross need
30 kg - 8 kg available - 10 kg confirmed = 12 kg to buy
12 kg / 5 kg per package = 2.4
Rounding: 3 packages, 15 kg in totalWhat to review before creating the order
The calculation says how much is missing according to the available data. It does not replace the purchasing assessment. An item may require a minimum lot, have a supplier whose lead time does not fit, or not fit in the storage space. Substituting an ingredient can change cost, yield and menu approval.
Separate a data entry error from a real change. An invalid yield, a missing conversion or a recipe sheet without a component must not become a silent estimate. A reliable calculation flags the open issue and leaves the item out of the suggestion until someone corrects it or approves an alternative.
- Shelf life and usability of the existing balance
- Storage capacity of the Unit
- Lead time and minimum quantity of each supplier
- Packaging and conversion to the base unit
- Items reserved for other services
- Menu changes made after the calculation
- Components without a valid recipe sheet, yield or share
Sources for this section: [5]
How MEPO handles this topic
In MEPO, the need can be calculated from the approved menu, recipe sheets and demand. The calculation takes into account available stock, reservations, open orders, the safety policy and packaging, keeps the origins and shows warnings. The team reviews the result and creates the request. The system does not buy automatically and does not estimate components that lack valid data.
References
The sources support the general concepts. Specific rules can vary by contract, technical lead and local regulations.
- [1]Planejamento de cardápios para a alimentação escolar (menu planning for school meals in Brazil). FNDE.
- [2]Manual da ferramenta Plan PNAE (manual for the Plan PNAE tool, from Brazil's national school meals programme). FNDE.
- [3]Resolução CFN nº 600/2018. Conselho Federal de Nutrição.
- [4]Ficha Técnica de Preparação: instrumento de qualidade (recipe sheet: a quality instrument). SciELO.
- [5]RDC nº 216/2004. Anvisa.