# How do I scale my recipe?

Scales every ingredient of a recipe from one number of servings to another, in exact fractions, with small cup amounts also in tablespoons and teaspoons.

- Page: https://www.acalculator.org/food/recipe-scaler
- JSON spec: https://www.acalculator.org/food/recipe-scaler.json
- Version: edf3f02b066c

## Default answer

Example with the default inputs (Recipe makes (servings) 4, Servings you want 6, Ingredients [Amount 2 1/4, Unit cup, Ingredient (optional) flour; Amount 1, Unit tsp, Ingredient (optional) baking soda; Amount 3/4, Unit cup, Ingredient (optional) sugar; Amount 1/2, Unit cup, Ingredient (optional) butter; Amount 2, Unit whole (count), Ingredient (optional) eggs]): Multiply each amount by 1 1/2 for 6 servings.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| from | Recipe makes (servings) | How many servings the recipe makes as written. |
| to | Servings you want | How many servings you want to make. |
| items | Ingredients | One row per ingredient: the amount as written, its unit, and its name. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| factor | Scale factor | Servings you want ÷ servings the recipe makes, as an exact fraction in lowest terms. |
| decimal | Scale factor (decimal) | The scale factor as a decimal. |
| scaled | Scaled ingredients | Each amount × the scale factor, with its unit and name. |

## Method

Scale factor = servings you want ÷ servings the recipe makes; each new amount = amount × scale factor, in the same unit.

## Assumptions

- Every ingredient scales by the same factor. Baking times, pan sizes, and strong flavours such as salt and spices may need judgment when you scale a lot.
- Amounts keep their unit. A cup amount under 1/4 cup also shows in tablespoons (1 cup = 16 tbsp), and a tablespoon amount under 1 also shows in teaspoons (1 tbsp = 3 tsp), US customary.
- Amounts with a denominator up to 16 show as fractions; others show as a decimal with 2 places.

## Worked examples

1. from = 4, to = 6, items = {"amount":"2 1/4","unit":"cup","name":"flour"} or {"amount":"1","unit":"tsp","name":"baking soda"} gives decimal = 1.5, scaled = 3 3/8 cups flour; 1 1/2 tsp baking soda; 1 1/8 cups sugar; 3/4 cup butter; 3 eggs. Source: NIST Handbook 44 (2026), Appendix C, General Tables of Units of Measurement (1 cup = 8 fl oz; 1 tablespoon = 1/2 fl oz; 1 teaspoon = 1/6 fl oz), https://www.nist.gov/document/2026-nist-handbook-44-appendix-c.
2. from = 12, to = 3, items = {"amount":"1/2","unit":"cup","name":"milk"} or {"amount":"1","unit":"tbsp","name":"oil"} gives decimal = 0.25, scaled = 1/8 cup milk (2 tbsp); 1/4 tbsp oil (3/4 tsp); 62 1/2 g flour. Source: NIST Handbook 44 (2026), Appendix C, General Tables of Units of Measurement (1 cup = 8 fl oz; 1 tablespoon = 1/2 fl oz; 1 teaspoon = 1/6 fl oz), https://www.nist.gov/document/2026-nist-handbook-44-appendix-c.
3. from = 6, to = 7, items = {"amount":"1","unit":"cup","name":"rice"} or {"amount":"0.5","unit":"l","name":"stock"} gives decimal = 1.166667, scaled = 1 1/6 cups rice; 7/12 L stock. Source: USDA FoodData Central (household measures: cup, tablespoon, teaspoon portions of foods), https://fdc.nal.usda.gov/.
4. from = 3, to = 10, items = {"amount":"1","unit":"tsp","name":"salt"} or undefined gives scaled = 3 1/3 tsp salt. Source: NIST Handbook 44 (2026), Appendix C, General Tables of Units of Measurement (1 cup = 8 fl oz; 1 tablespoon = 1/2 fl oz; 1 teaspoon = 1/6 fl oz), https://www.nist.gov/document/2026-nist-handbook-44-appendix-c.
5. from = 20, to = 3, items = {"amount":"1","unit":"cup","name":"water"} or undefined gives scaled = about 0.15 cup water (2 2/5 tbsp). Source: NIST Handbook 44 (2026), Appendix C, General Tables of Units of Measurement (1 cup = 8 fl oz; 1 tablespoon = 1/2 fl oz; 1 teaspoon = 1/6 fl oz), https://www.nist.gov/document/2026-nist-handbook-44-appendix-c.

## FAQ

### How do I scale a recipe?

Divide the servings you want by the servings the recipe makes to get the scale factor, then multiply every ingredient by it. From 4 servings to 6 the factor is 6 ÷ 4 = 1 1/2, so 2 1/4 cups of flour become 3 3/8 cups.

### How do I halve or double a recipe?

To double, the factor is 2; to halve, 1/2. Type the recipe’s servings and twice or half as many, or type 1 and 2 (or 2 and 1) to scale by 2 or 1/2 directly.

### How many tablespoons are in a cup?

16 tablespoons are in 1 cup, and 3 teaspoons are in 1 tablespoon (US customary measures). So 1/8 cup is 2 tablespoons, and 1/4 tablespoon is 3/4 teaspoon. The scaler shows these for small amounts.

### Why do some amounts show as “about” a decimal?

Fractions with a denominator up to 16 (halves, thirds, quarters, eighths, sixteenths, and so on) show exactly. Others, such as 3/20 cup, show as a decimal to 2 places, 0.15, because no measuring cup marks them.

### Does everything scale the same way?

The arithmetic does, but cooking does not always. Baking times, pan sizes, leavening, salt and spices may need judgment when you scale by a lot. Eggs may need rounding to a whole egg.

### Can I type decimals and mixed numbers?

Yes. Type 2, 0.5, 3/4 or 1 1/2 (a space before the fraction). The page works with the exact values you type.

## Sources

- NIST Handbook 44 (2026), Appendix C, General Tables of Units of Measurement (US customary: 1 cup = 8 fluid ounces, 1 tablespoon = 1/2 fluid ounce, 1 teaspoon = 1/6 fluid ounce). https://www.nist.gov/document/2026-nist-handbook-44-appendix-c (retrieved 2026-10-01)
- USDA FoodData Central (foods listed with household measures in cups, tablespoons and teaspoons). https://fdc.nal.usda.gov/ (retrieved 2026-10-02)