Recipe Scaler

About this calculator

A recipe scaler takes a list of ingredients written for one batch size and rewrites it for any other batch size. It is the same arithmetic you would do by hand — multiply each amount by the same factor — but it handles two things that are tedious to do mentally: parsing mixed units (cups, tablespoons, grams, millilitres, fractions), and rounding the result to a fraction you can actually measure with standard kitchen tools.

The calculator works on the whole ingredient list at once. You type the original number of servings the recipe makes, the target number of servings you want, and then your ingredients. As you type, every ingredient gets the new amount filled in beside it. There is no 'scale' button; the conversion happens live. Quick-multiplier chips (½×, 2×, 3×) cover the common cases without doing the division in your head.

This is the right tool for adjusting a four-serving weeknight recipe up to feed eight at a dinner party, or for cutting a Christmas-cookie recipe in half because you do not need ninety cookies. For the cases where straight multiplication does not work — eggs, salt and spices, leavening, very large batches — see the kitchen notes below the calculator.

The math behind recipe scaling

Recipe scaling is a single-factor linear transformation: scale_factor = target_servings ÷ original_servings, then new_amount = original_amount × scale_factor for every ingredient.

Worked example. A bread recipe calls for 4 cups flour, 1½ cups water, 2 tsp salt, and 1 tsp instant yeast, makes 16 slices, and you want 24 slices. Factor = 24 ÷ 16 = 1.5. Scaled: 6 cups flour, 2¼ cups water, 3 tsp salt, 1½ tsp yeast. The calculator does exactly this multiplication and then renders the results in readable fractions (¼, ⅓, ½, ⅔, ¾) instead of decimal values like 0.333… cups.

A few ingredients break this linear rule. Eggs come in whole units; salt and strong spices behave non-linearly because of how taste perception works (doubling salt does not feel like 'twice as salty' — it feels much saltier than that); leavening agents (baking soda, baking powder, yeast) need slight downward adjustment in very large batches because excess leavening can cause collapse. The calculator gives you the mathematically scaled amount; the kitchen-notes section below tells you which ones to fine-tune by hand.

Before you scale — a few kitchen notes

Equipment matters as much as quantity. If you scale a recipe up but keep the same pan, the batter or dough sits deeper and may cook unevenly — the centre stays raw while the edges over-brown. Either split the larger batch across two pans, or use a deeper pan and add baking time (5–10 minutes per inch of extra depth, and start checking 10 minutes early).

For very large scale factors (3× and up), test with a smaller batch first. Cake recipes especially can change character when scaled aggressively — the ratio of crust to crumb shifts, leavening becomes less reliable, and the central temperature climbs more slowly. Restaurant bakers rarely 'scale up' a home-style cake recipe; they use a different formula sized for production. For 1.5× or 2× scaling at home, you can almost always trust straight multiplication.

For very small scale factors (¼× or less), liquid measurements get hard. A ¼ tsp split four ways is below what most measuring spoons can read. Either round up to the smallest measurable amount, skip the ingredient if it is purely a flavour accent (a pinch of nutmeg, for example), or measure by weight in grams using a kitchen scale.

For batch cooking and meal-prep portions, treat the scaler as a starting point and adjust to the equipment you actually have. A doubled lasagne fits a 9×13 pan; tripled, it does not. A doubled soup needs a stockpot, not a saucepan. The math is the easy part; matching it to your kitchen is where judgement comes in.