Doubling a recipe sounds simple until you hit “1 1/2 cups flour” and have to work out what one-and-a-half times one-and-a-half actually is, in your head, while your hands are covered in batter. Our Recipe Scaler does that arithmetic for an entire ingredient list at once.
How it parses quantities
Paste in a recipe, one ingredient per line, and the scaler looks for a leading quantity in any of three common formats:
- Decimal, like
0.5 tsp salt - Simple fraction, like
1/2 cup sugar - Mixed number, like
1 1/2 cups flour
Whatever comes after that number — the unit and ingredient name — is left untouched; only the quantity is recalculated.
Lines without a number pass through unchanged
Not every line in a recipe has a measurable quantity. “Salt to taste,” a section header like “For the glaze:”, or plain instructions don’t start with a number, so the scaler leaves them exactly as written rather than erroring out or mangling them.
A worked example
With the default 4 → 6 servings (a scaling factor of 1.5):
2 cups flour→3 cups flour1 cup sugar→1.5 cup sugar0.5 tsp salt→0.75 tsp salt3 eggs→4.5 eggs1.5 tbsp vanilla extract→2.25 tbsp vanilla extract
And with mixed numbers and fractions specifically: 1 1/2 cups flour scales to 2.25 cups flour, and 2/3 cup milk scales to 1 cup milk — both computed the same way as any decimal quantity, just parsed from a different input format first.
Rounding, and scaling down
Results are rounded to two decimal places with trailing zeros trimmed, so you get clean numbers like 3 rather than 3.00. Very awkward measurements (like 0.33 cups) are shown as-is rather than converted to the nearest “kitchen-friendly” fraction — that conversion isn’t automated, so you may need to eyeball an odd result to the nearest measuring cup marking. And scaling works in both directions: set a target serving count smaller than the original to shrink a recipe down, using the exact same math.
Try it yourself: Recipe Scaler.