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Recipe Scaler

Calculators · Added

Paste an ingredient list and change the number it serves. Quantities written as fractions, decimals, mixed numbers or the ½-style characters printed in cookbooks are all read, and the results come back snapped to fractions a measuring cup actually has.

One ingredient per line, quantity first. Fractions, decimals and ½-style characters all work.

Scale by
Write fractions as

For a cake — the tin has to grow by area, not by length

How to use the recipe scaler

  1. 1Paste the ingredient list, one item per line, with the quantity at the start of each line.
  2. 2Say what the recipe serves and what you need it to serve — or switch to a plain multiplier.
  3. 3Read the scaled list, and check the lines marked unchanged: those had no quantity to scale.
  4. 4Copy the result, and read the note about what scaling does not change before you start cooking.

Examples

Four servings into six

Input
2 cups flour · 1 1/2 tsp baking powder · ½ tsp salt
Result
3 cups flour · 2¼ tsp baking powder · ¾ tsp salt

A line with nothing to scale

Input
Salt and pepper to taste
Result
Passed through unchanged, and flagged as such

About the recipe scaler

Why fractions rather than decimals

Multiplying ¾ cup by 1.5 gives 1.125 cups, which is a true answer and a useless one — no measuring cup has that mark. Rounded to the eighths that kitchen equipment does have, it is 1⅛ cups, which you can actually measure.

So results are snapped to halves, thirds, quarters, sixths and eighths, and only fall back to a decimal where none of those is within a per cent. Thirds are kept as thirds rather than becoming 0.33 because measuring spoons come in thirds and decimals do not.

Where scaling stops working

Beyond about four times, a recipe usually needs rethinking rather than multiplying. Pans and ovens have limits; a volume of batter that fits nowhere has to be baked in batches, and batches behave differently from one large bake. Reduction sauces are worse still, since evaporation depends on surface area and the pan's surface does not grow with the volume in it.

Baking is where scaling is most reliable and most demanding at once, because the ratios matter more than in almost any other cooking. Working by weight rather than by volume is what makes a scaled bake repeatable — cups measure volume, and a cup of flour can vary by twenty per cent depending on how it was filled.

Frequently asked questions

Does the cooking time scale too?
No, and this is the mistake worth avoiding. A doubled cake batter in a bigger tin is deeper, not twice as thick, and needs perhaps a quarter longer rather than twice as long. A doubled roast is barely longer at all. Time follows how far heat has to travel into the food, so judge by internal temperature and by look — never by the multiplier.
What size tin do I need if I double a recipe?
One with twice the area, which means about 1.41 times the diameter — a 20 cm round tin becomes 28 cm, not 40 cm. The tool works this out if you enter the original diameter. Getting it wrong in the other direction is worse: batter for two in a tin for one overflows, and what stays in bakes unevenly.
Should everything really be multiplied?
Quantities, yes. Judgement, no. Salt, spices, yeast and chemical leavening are all commonly held back when a recipe is scaled up, because neither the perception of seasoning nor the rate of a reaction is proportional to mass. Scale them with everything else, then taste before committing.
What do I do with two thirds of an egg?
Beat one and weigh out the share. A large egg is around 50 g out of its shell, so two thirds is about 33 g, and the yolk-to-white ratio stays right if it is properly mixed first. The arithmetic is correct; it is just not something you can measure in whole units.

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