How this calculator works
Dry pasta is made from flour and water and contains very little water itself. When boiled, the starch granules take up water and swell, so the same pieces become heavier and larger. A typical dry pasta gains 1.2 to 1.8 times its weight in water, giving a cooked mass about 2.2 to 2.8 times the dry mass. Long and short semolina shapes are similar, egg noodles gain less, and small shapes such as orzo absorb more and pack more densely in a cup.
Formula
cooked mass = dry mass x yield. dry mass = cooked mass / yield. A US cup of dry long pasta weighs about 91 g and a cup of cooked pasta about 140 g. The yields used here are 2.5 for long pasta, 2.45 for short pasta, 2.2 for egg noodles and 2.8 for orzo.
Worked example
A recipe uses 2 oz (56.7 g) of dry spaghetti. At a yield of 2.5 the cooked mass is 141.8 g, which is 141.8 / 140 = 1.01 cups, matching the familiar guidance that 2 oz of dry spaghetti makes about one cup cooked. Starting from 250 g of cooked penne, the dry mass is 250 / 2.45 = 102 g, or 1.13 cups dry.
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Frequently asked questions
How much does pasta grow when cooked?
Most dried semolina pasta roughly doubles and a half in mass. That is why a 100 g portion of dry pasta becomes about 250 g cooked. The exact gain depends on the shape, the cooking time and how much water the pasta is allowed to absorb.
Is 2 oz of dry pasta one serving?
It is the traditional single serving on Italian pasta packaging, about 56.7 g dry and roughly 140 g cooked. Appetites and meal context vary, so treat it as a reference rather than a rule.
Why do egg noodles give a different result?
Fresh and dried egg noodles contain egg solids and less starch, and they absorb less water than semolina pasta. Their cooked mass is about 2.2 times the dry mass rather than 2.5.
Should I salt the water or add oil?
Salt the water for flavour; it does not change the dry-to-cooked ratio materially. Oil does not prevent sticking in the pot and can keep sauce from clinging, so it is better left out.