Scale a recipe by its required yield, not by a guess at extra ingredients. First confirm both the number of portions and the size of each portion. This original classroom example uses prepared fruit weights to show why 30 portions can require two different conversion factors.
Start with a clearly defined batch
Our fictional worksheet makes 12 portions of 150 g each: 1,800 g altogether. It contains 1,200 g of prepared melon, 480 g of prepared apple and 120 g of prepared grapes. These are invented teaching quantities, not a tested production recipe. Assume no further weight loss in this arithmetic exercise.
The BC Cook Articulation Committee's recipe-conversion chapter explains the conversion-factor method: divide the required yield by the original yield, then multiply ingredient quantities by that factor. When portion size changes, compare total yields in matching units.
Make 30 portions at the same size
The order is for 30 portions, still 150 g each. Required yield is 30 × 150 g, or 4,500 g. The factor is 4,500 ÷ 1,800: 2.5. Because the portion size is unchanged, 30 ÷ 12 gives the same factor.
- Prepared melon: 1,200 g × 2.5 gives 3,000 g.
- Prepared apple: 480 g × 2.5 gives 1,200 g.
- Prepared grapes: 120 g × 2.5 gives 300 g.
Check the total: 3,000 + 1,200 + 300 is 4,500 g. Divide that by 30 and each portion is 150 g. Write both checks on the worksheet; an ingredient calculation can look plausible while the final portion size is wrong.
Recalculate when the portion size changes
In a separate variation, the trainer requests 30 smaller portions of 120 g. The required total is now 3,600 g. Divide 3,600 by the original 1,800: the factor is 2, giving 2,400 g melon, 960 g apple and 240 g grapes.
Using 2.5 again would prepare 4,500 g, which is 900 g more than this variation requires. The portion count did not change; the agreed portion size did. A useful read-back is: “Thirty portions at 120 g, total 3.6 kg, conversion factor two.”
Keep preparation weights separate from purchasing
The quantities above describe usable prepared ingredients. They do not tell a buyer how much whole fruit to order. The committee's yield-testing chapter distinguishes purchased weight from usable product after preparation losses. A real purchasing calculation needs the relevant measured yield; do not invent a universal peeling or trimming percentage.
Check the worksheet before using it
- Record the original recipe version, yield and portion size.
- Confirm the requested portions and size with the responsible colleague.
- Use one consistent unit for each calculation and keep decimal values until the final measurement decision.
- Reconcile ingredient totals with the intended batch and portion weights.
- Ask the supervising chef to test and authorize any production change.
Scaling arithmetic does not establish cooking times or equipment suitability. The conversion chapter cautions that seasonings and cooking or mixing times may need adjustment. Follow the kitchen's tested recipe and food-safety procedures; this exercise contains no cooking method.
Practise explaining why 2.5 and 2 are both correct for different requests. For wider restaurant-service skills, explore HCA food and beverage service training.
Explore HCA food and beverage service training
