Quick answer
The scale factor = desired servings ÷ original servings, and each ingredient is multiplied by it. Scaling a 4-serving recipe to 6 gives a factor of 1.5, so 2, 0.5 and 1.25 become 3, 0.75 and 1.875.
Enter the original and desired servings and the ingredient amounts. The calculator returns the factor and scaled amounts.
Related tools: Nutrition per Serving Calculator: Nutrients per serving from recipe totals. Recipe Cost Calculator: Total recipe cost from ingredient costs. Cooking Ingredient Converter: Convert between volume and weight for common baking and cooking ingredients, using USDA gram weights per cup.
How to use the Recipe Scaling Calculator
- Enter original servings (above 0).
- Enter desired servings (above 0).
- Type ingredient amounts, for example 2, 0.5, 1.25.
- Press Calculate to see the result, and use Reset to start again.
| Input | What to enter | Allowed values |
|---|---|---|
| Original servings | A number | > 0 |
| Desired servings | A number | > 0 |
| Ingredient amounts | Text, such as 2, 0.5, 1.25 | — |
Formula and method
Formula
factor = desired ÷ original servings
IEEE-754 double precision; shown to the decimals indicated.
Cooking times and pan sizes may need adjusting for large changes.
Worked examples
These examples are verified: each one is an automated test case that the live calculator must reproduce exactly.
Example 1
Inputs: Original servings = 4; Desired servings = 6; Ingredient amounts = 2, 0.5, 1.25.
| Result | Value |
|---|---|
| Scale factor | 1.5 |
| Scaled amounts | 3, 0.75, 1.875 |
Example 2
Inputs: Original servings = 12; Desired servings = 8; Ingredient amounts = 3, 1.5.
| Result | Value |
|---|---|
| Scale factor | 0.6667 |
| Scaled amounts | 2, 1 |
Example 3
Inputs: Original servings = 6; Desired servings = 6; Ingredient amounts = 1.
| Result | Value |
|---|---|
| Scale factor | 1 |
| Scaled amounts | 1 |
The first line is the headline result (scale factor). Below it the recipe Scaling Calculator lists scaled amounts, which describe the same case from other angles. IEEE-754 double precision; shown to the decimals indicated.
What does not scale
Spices, salt, leavening and thickeners often do not scale linearly, especially for large increases. Start with about 75% of the scaled amount of strong spices and adjust to taste.
Pans and times
A bigger batch needs a bigger pan, and cooking times change: a doubled cake in the same pan will be deeper and take longer. Use the Cake Pan Size calculator to scale baking pans.
How the result changes with original servings
Holding every other input at the first worked example, this table changes only original servings. It shows how sensitive the answer is to that one value; each row was produced by running this calculator.
| Original servings | Scale factor | Scaled amounts |
|---|---|---|
| 2 | 3 | 6, 1.5, 3.75 |
| 4 | 1.5 | 3, 0.75, 1.875 |
| 8 | 0.75 | 1.5, 0.375, 0.938 |
| 16 | 0.375 | 0.75, 0.188, 0.469 |
What happens with invalid input
These messages are produced by the calculator itself, so you know what to fix.
- Original servings: entering "0" shows "Original servings must be greater than 0." beside that field and no result.
- Ingredient amounts: left empty shows "Enter ingredient amounts." beside that field and no result.
Choosing between the Recipe Scaling Calculator and similar calculators
Each row shows what a related calculator on this site asks for and what it returns, so you can pick the one that matches your question.
| Calculator | You enter | It returns |
|---|---|---|
| [Nutrition per Serving Calculator](/cooking/nutrition-per-serving-calculator/) | total calories, total protein and total carbohydrate | Calories per serving |
| [Recipe Cost Calculator](/cooking/recipe-total-cost-calculator/) | cost of each ingredient | Total cost |
| [Cooking Ingredient Converter](/cooking/cooking-ingredient-converter/) | ingredient, convert and amount | Weight |
| [Brine Concentration Calculator](/cooking/brine-concentration-calculator/) | salt and water | Brine concentration |
| [Cost per Serving Calculator](/cooking/cost-per-serving-calculator/) | total cost and servings | Cost per serving |
Background: cooking measurements
For baking, weight is more reliable than volume. A cup holds a fixed volume but its weight depends on the ingredient's density, and a cup of flour can vary by 20 to 30 grams depending on how it is scooped, so published gram-per-cup values for the same ingredient differ from site to site. Spoon and level flour if you must measure by volume.
Check which cup a recipe uses: the US cup is 236.588 mL, while a metric cup is 250 mL.
Assumptions and limitations
- Spices and leavening may not scale linearly
Cooking times are guides. Use a food thermometer to confirm safe internal temperatures.
If a required value is empty, not a number, or outside its allowed range, the form marks that field with a message and shows no result instead of a misleading number. The automated checks deliberately try invalid entries for original servings and ingredient amounts to confirm this.
Frequently asked questions
Can I halve a recipe with an egg?
Beat the egg and use half by weight or volume.
Does the cooking time change?
Often, check for doneness.
What is a factor of 1.5?
Fifty percent more than the original.
What does the Recipe Scaling Calculator calculate?
Scale ingredient amounts to a different number of servings. It returns Scale factor and Scaled amounts.
What formula does the Recipe Scaling Calculator use?
factor = desired ÷ original servings. Cooking times and pan sizes may need adjusting for large changes.
What do I need to enter in the recipe Scaling Calculator?
You enter Original servings, Desired servings and Ingredient amounts.
How is the result rounded or limited?
IEEE-754 double precision; shown to the decimals indicated. Spices and leavening may not scale linearly.
What is an example of a recipe Scaling result?
With original servings 4, desired servings 6 and ingredient amounts 2, 0.5, 1.25, the scale factor is 1.5.
Can I rely on this calculator for a decision?
Cooking times are guides. Use a food thermometer to confirm safe internal temperatures. For this calculator in particular: Spices and leavening may not scale linearly.
Related calculators
- Nutrition per Serving Calculator — Nutrients per serving from recipe totals.
- Recipe Cost Calculator — Total recipe cost from ingredient costs.
- Cooking Ingredient Converter — Convert between volume and weight for common baking and cooking ingredients, using USDA gram weights per cup.
- Brine Concentration Calculator — Salt concentration of a brine by weight.
- Cost per Serving Calculator — Cost of one serving.
- Food Waste Percentage Calculator — Share of food that was wasted.
Sources
- OpenStax, Prealgebra 2e (Rice University): fractions, decimals, percents, ratios and rounding
- NIST Special Publication 811, Guide for the Use of the International System of Units (SI), Appendix B conversion factors (international inch 25.4 mm, avoirdupois pound 0.45359237 kg)
Content last reviewed 2026-11-04. Formulas and worked examples are checked by automated tests against independently computed values.