What it does
The Recipe Fraction Scaling Calculator resizes any fractional ingredient amount when you change how many servings you are making. Enter the original quantity as a whole number plus a fraction (for example 1 and 1/2), tell it the original and new serving counts, and it returns the scaled amount as both a decimal and a tidy kitchen fraction rounded to the nearest 1/16.
How to use it
Type the whole-number part (use 0 if none), the numerator, and the denominator of your ingredient amount. Then enter the servings the recipe was written for and the servings you actually want. Press calculate to see the new amount.
The formula explained
First the mixed number is converted to a single value: \(\text{original} = \text{whole} + \frac{\text{numerator}}{\text{denominator}}\). Then a scaling factor is found by dividing the new servings by the old servings. Multiplying the original amount by that factor gives the new amount. The result is snapped to the nearest sixteenth so it maps to common measuring spoons and cups.
$$\begin{gathered} \text{New Amount} = A \times \frac{\text{New Servings}}{\text{Original Servings}} \\[1.5em] \text{where}\quad A = \text{Whole} + \frac{\text{Numerator}}{\text{Denominator}} \end{gathered}$$
Worked example
Scaling 3/4 cup from 4 to 6 servings: original = 0 + 3/4 = 0.75. Factor = 6 / 4 = 1.5. New amount = 0.75 × 1.5 = 1.125 cups, which is about 1 1/8 cups.
$$0 + \frac{3}{4} = 0.75 \qquad \frac{6}{4} = 1.5 \qquad 0.75 \times 1.5 = 1.125$$
FAQ
Can I halve a recipe? Yes — set new servings to half the original (e.g. old 4, new 2) and the factor becomes 0.5.
Why is my answer rounded? Kitchen tools measure in fractions like 1/8 and 1/16, so the displayed fraction is rounded to the nearest 1/16 while the raw decimal stays exact.
Does it work for any unit? Yes. The math is unitless, so it works for cups, teaspoons, grams, or ounces alike.
