# Điều chỉnh lượng nguyên liệu

> Scale a recipe to any number of servings: each ingredient is multiplied by new ÷ original servings, with cups and spoons shown as kitchen fractions.

Phiên bản tương tác: https://www.calcopenly.com/vi/everyday/recipe-scaler
Chủ đề: Máy tính hằng ngày

Every amount is multiplied by the scale factor: the servings you need divided by the servings the recipe makes. Cup, spoon and count amounts are rounded to the nearest measure a kitchen set holds (eighths, quarters, thirds and halves) and marked ≈ when rounded. Grams, kilograms, millilitres and litres stay as decimals.

The default recipe goes from 4 to 6 servings, a factor of 1.5, so 3/4 cup of sugar becomes 1 1/8 cups and 250 g of butter becomes 375 g. The Institute of Child Nutrition teaches the same two steps for school kitchens: 35 servings from a 25-serving recipe is a factor of 1.4, which turns 3 cups of tomatoes into 4.2 cups, rounded to 4 1/4.

Lines without a number, such as "salt to taste", are kept as written. Baking time, pan size and seasoning do not scale in proportion, so check them separately.

## Dữ liệu đầu vào

- **Ingredients, one per line**: Start each line with the amount: 2, 1 1/2, 3/4, 1.5 or ½. Lines without an amount are kept as written.
- **Recipe makes (servings)**
- **Servings you need**

## Kết quả

- Scale factor — kết quả chính
- Scaled recipe
- Lines scaled
- Lines kept as written

## Công thức

$$
\text{new} = \text{old} \times \frac{\text{servings needed}}{\text{servings made}}
$$

## Ví dụ có lời giải

### Default recipe from 4 to 6 servings

- Ingredients, one per line: 2 cups flour / 1 1/2 tsp salt / 3/4 cup sugar / 2 eggs / 1/3 cup milk / 250 g butter
- Recipe makes (servings): 4
- Servings you need: 6
- **Scale factor: 1.5**
- **Scaled recipe: 3 cups flour; 2 1/4 tsp salt; 1 1/8 cup sugar; 3 eggs; 1/2 cup milk; 375 g butter**
- Nguồn đối chiếu: Python fractions: 2×3/2 = 3, 3/2×3/2 = 9/4, 3/4×3/2 = 9/8, 1/3×3/2 = 1/2, 250×3/2 = 375

### Halving

- Ingredients, one per line: 1 cup sugar / 2 tbsp butter / 1 egg
- Recipe makes (servings): 4
- Servings you need: 2
- **Scale factor: 0.5**
- **Scaled recipe: 1/2 cup sugar; 1 tbsp butter; 1/2 egg**
- Nguồn đối chiếu: Python fractions: each amount × 1/2

### Unscaled line, unicode fraction, range and an approximate fraction

- Ingredients, one per line: Salt to taste / 1½ cups oats / 2-3 cloves garlic / 1 cup milk
- Recipe makes (servings): 6
- Servings you need: 5
- **Scaled recipe: Salt to taste; 1 1/4 cups oats; 1 2/3–2 1/2 cloves garlic; ≈ 7/8 cup milk**
- **Lines kept as written: 1**
- **Lines scaled: 3**
- Nguồn đối chiếu: Python fractions: 3/2×5/6 = 5/4; 2×5/6 = 5/3, 3×5/6 = 5/2; 5/6 = 0.833 is nearest 7/8 among eighths and thirds

### 25 to 35 servings (ICN worked example)

- Ingredients, one per line: 3 cups tomatoes
- Recipe makes (servings): 25
- Servings you need: 35
- **Scale factor: 1.4**
- **Scaled recipe: ≈ 4 1/4 cups tomatoes**
- Nguồn đối chiếu: Institute of Child Nutrition, Adjusting Standardized Recipes: 35 ÷ 25 = 1.4; 3 cups × 1.4 = 4.2 cups, rounded to 4 ¼ cups

### Decimal metric amounts

- Ingredients, one per line: 125 g sugar / 0.5 L stock
- Recipe makes (servings): 4
- Servings you need: 3
- **Scale factor: 0.75**
- **Scaled recipe: 93.75 g sugar; 0.38 L stock**
- Nguồn đối chiếu: Hand calculation: 125 × 0.75 = 93.75; 0.5 × 0.75 = 0.375, shown to 2 decimals (half-up)

## Câu hỏi

### How do you scale a recipe up or down?

Divide the servings you need by the servings the recipe makes, then multiply every ingredient by that factor. Going from 4 to 6 servings is a factor of 1.5, so 2 cups of flour becomes 3 cups; going from 4 to 2 is 0.5. The Institute of Child Nutrition advises converting mixed amounts such as 1 lb 8 oz to one unit (1.5 lb) before multiplying.

### What is half of 1/3 cup or 3/4 cup?

Half of 1/3 cup is 1/6 cup: 2 tablespoons plus 2 teaspoons, because a US cup holds 16 tablespoons and a tablespoon holds 3 teaspoons. Half of 3/4 cup is 3/8 cup, or 6 tablespoons. When no standard measure matches, the calculator shows the nearest eighth or third with ≈ and gives the exact decimal in the table.

### Does baking time change when you double a recipe?

Often, because baking time depends on the depth of the batter more than on its amount. Doubled batter in the same pan is twice as deep and needs longer; spread over a pan with twice the area, it keeps its depth and bakes in close to the original time. Keep the oven temperature the same and test for doneness early.

### Is a cup the same size in every country?

No. A US customary cup is 8 US fluid ounces, 236.6 mL, while the metric cup used in Australia and New Zealand is 250 mL, about 6% larger. Scaling works the same in both systems because every amount is multiplied by the same factor. NIST advises weighing ingredients on a kitchen scale for accuracy rather than measuring by volume.

### “Điều chỉnh lượng nguyên liệu” chính xác đến mức nào?

Độ chính xác phụ thuộc vào dữ liệu nhập và giả định của phương pháp. Phép tính thập phân dùng 50 chữ số có nghĩa, nhưng ước lượng, phương pháp số và dữ liệu nguồn có thể kém chính xác hơn; làm tròn khi hiển thị không loại bỏ các giới hạn đó. Ví dụ có lời giải đã đối chiếu với nguồn độc lập: 5. Ví dụ, “Default recipe from 4 to 6 servings” được kiểm tra bằng Python fractions: 2×3/2 = 3, 3/2×3/2 = 9/4, 3/4×3/2 = 9/8, 1/3×3/2 = 1/2, 250×3/2 = 375.

### Phương pháp này lấy từ đâu?

Institute of Child Nutrition — Adjusting standardized recipes (factor = new yield ÷ old yield); NIST Metric Kitchen — Culinary measurement tips.

## Nguồn

- [Institute of Child Nutrition — Adjusting standardized recipes (factor = new yield ÷ old yield)](https://theicn.org/cacfp-itrain-simple-lesson-plans/training-scripts/Adjusting-Standardized-Recipes.pdf)
- [NIST Metric Kitchen — Culinary measurement tips](https://www.nist.gov/pml/owm/metric-si/metric-kitchen/metric-kitchen-culinary-measurement-tips)