To calculate catering quantities, work out portions per guest, add a contingency, then round up to whole packs or batches. Write each step so a marker can follow it.
This lesson sits in the SPM subjects and learning resources section, under Catering and Serving.
The four-step method
- Portions: guests multiplied by portions per guest.
- Contingency: add a stated percentage for spoilage and extra helpings.
- Convert: change the total into the unit you buy or cook in.
- Round up: to whole packs, trays or batches.
Put each step on its own line, with a short label. A planner who skips a step loses the reader.
Worked example: a tea reception for 80 guests
This is a fictional event, used only to show the method. A school business club holds a tea reception for 80 guests.
Kuih. Plan for 2 pieces per guest.
- Step 1: 80 × 2 = 160 pieces.
- Step 2: contingency of 10%: 160 × 0.10 = 16, so 160 + 16 = 176 pieces.
- Step 3: the kuih comes in trays of 24, so 176 ÷ 24 = 7.33 trays.
- Step 4: round up to 8 trays, which gives 192 pieces.
Tea. Plan for 1.5 cups per guest, 200 ml per cup.
- Step 1: 80 × 1.5 = 120 cups.
- Step 2: contingency of 10%: 120 × 1.10 = 132 cups.
- Step 3: 132 × 200 ml = 26 400 ml = 26.4 litres.
- Step 4: round up and prepare 27 litres.
Scaling a recipe. A cake recipe serves 12 and uses 360 g of flour. For 80 portions:
- Scale factor = 80 ÷ 12 = about 6.67.
- Flour = 360 × 6.67 = about 2 400 g, or 2.4 kg.
Quick check: 12 portions use 360 g, so 1 portion uses 30 g. Then 80 × 30 = 2 400 g. Both routes agree.
The mistake that costs marks
The usual slip is multiplying every ingredient by the number of guests. The recipe already feeds 12, so 360 g × 80 gives 28 800 g of flour, which is far too much.
| Step | Wrong | Right |
|---|---|---|
| Scale factor | 80 (guests) | 80 ÷ 12 = 6.67 |
| Flour | 360 × 80 = 28 800 g | 360 × 6.67 = about 2 400 g |
| Sense check | Not done | 28.8 kg flour for 80 slices cannot be right |
The fix is to ask before multiplying: how many people does this recipe already serve?
Where to show the working
In a written planning answer, list the assumptions first: guests, portions, contingency, pack size. Then show each calculation on its own line, then a summary table of what to buy.
| Item | Needed | Pack size | Buy |
|---|---|---|---|
| Kuih | 176 pieces | 24 per tray | 8 trays |
| Tea | 26.4 litres | per litre | 27 litres |
| Flour | 2.4 kg | 1 kg bags | 3 bags |
A clear table lets a marker see each number and give credit for it.
Check yourself
A fictional school dinner has 45 guests.
- Each guest gets 3 sandwiches.
- The plan adds 10% contingency.
- One loaf makes 10 sandwiches.
How many loaves should be bought?
Answer
Portions: 45 × 3 = 135 sandwiches.
Contingency: 135 × 0.10 = 13.5, so 135 + 13.5 = 148.5, which rounds up to 149 sandwiches.
Loaves: 149 ÷ 10 = 14.9, so round up to 15 loaves.
Check: 15 loaves make 150 sandwiches, which covers 149.
What to study next
Go on to justifying a menu and service sequence in a fictional scenario, then test your structure with the structured-answer self-review tool.
Practical cooking and serving work is assessed by your school. If you want a teacher to go through planning calculations with you, see online one-to-one Catering and Serving tuition.