How To Scale A Recipe Calculator
Scaling a recipe is one division followed by a great many multiplications. The division is trivial; knowing which ingredients should not be multiplied at all is the actual skill.
Scale factor
1.5
- The ingredient at the new scale
- 375
- Amount per single serving
- 62.5
- The same ingredient for twelve servings
- 750
Values update as you type. This calculator covers the single scenario its formula assumes — see Common Mistakes for what it leaves out.
The formula this calculator uses
Scale factor = desired servings / original servings, then new amount = original amount x factor
- desired
- Servings you want to end up with
- original
- Servings the recipe as written makes
- factor
- Unitless ratio, desired divided by original
- amount
- The quantity of one ingredient, before or after scaling
How to check the result by hand
- 1
Write down the two serving counts
Find the number of servings the recipe makes and the number you want, and put them in the right order. Four and six in the standard example. Swapping them inverts the factor, turning 1.5 into 0.6667 and shrinking a recipe you meant to enlarge.
- 2
Divide to get the scale factor
Desired divided by original: 6 / 4 = 1.5. A factor above one enlarges the recipe, below one shrinks it, and exactly one leaves it alone. This single number now governs every line that follows, so it is worth confirming before you touch the ingredients.
- 3
Multiply every proportional ingredient by the factor
250 g becomes 250 x 1.5 = 375 g, and the same multiplication runs down the whole list. The amount per serving should stay fixed at 62.5 g, which is your running check on each line. Work in one unit system throughout, because mixing cups with grams introduces an error the factor cannot see.
- 4
Trim the ingredients that are not linear
Leaveners, salt, strong spices, eggs and alcohol do not want the full factor. Add leaveners at roughly three-quarters of the increase, season to taste at the very end, and weigh beaten egg for the awkward fractions. This step is judgement rather than arithmetic, and it is where most scaled recipes go wrong.
- 5
Match the pan by area and set the time by observation
If the tin changes, scale by the ratio of the squared diameters, so moving from 8 inches to 10 inches means 1.5625 rather than 1.25. Keep the stated oven temperature and judge doneness by eye and texture, because time lengthens by a fraction of the factor rather than by all of it.
For worked examples, common mistakes and the limits of this formula, read the full How To Scale A Recipe page.