There are 600 different varieties of pasta; even if you chalk 90% of them up to regional preference or marketing decisions, that still leaves a lot of variation to explain. Here’s some research I’ve conducted on why there are so many different pasta shapes and when you might want to use one or the other.

Understanding the functions of the basic pasta shapes

As a general taxonomy, you can split pasta up into a few archives: strands, shapes and tubes, and sheets.

Sheets are fairly easy to explain; they’re made for dishes like lasagna that are prepared as casseroles or as pies, rather than as a dish that’s eaten from a bowl with just a fork. Some have ruffles, I assume for sauce retention.

Strands are a pretty simple shape, right? The main variation among them is thickness.

• Thin strands are meant for light sauces, like a simple angel hair with olive oil and garlic, or perhaps a thin tomato sauce. Otherwise, the strands get lost in the sauce, and you don’t get their texture at all. Also, with thin strands, the lubrication provided by thinner and oil-based sauces helps keep the strands from sticking together.

• Thick strands are meant for heavy sauces. There’s a reason it’s fettucine alfredo, and not angel hair alfredo. (I think putting it this way does the best job of explaining the difference. If there were angel hair in your alfredo, would you even notice its presence?)

• Spaghetti is kind of in the middle, and is a nice all-purpose pasta for this reason. If you are really detail-oriented, you can look for square spaghetti, which has slightly more surface area for sauce to stick to.

For tubes and shapes, the main variation is also by size.

• Very small tubes, like ditalini, and small shapes, like orzo or even alphabet pasta, are meant for soup. Some authorities make distinctions between pasta for soup and pasta for broth, but I won’t get into that here.

• The bigger the shape or tube gets, the heartier the sauce you can serve it with. So rigatoni, for example, could be good with a bolognese because the tubes are big enough to fill up with sauce and ground meat. Note that apparently spaghetti bolognese is not really served within Italy.

• The giant shapes, like giant shells, are meant to be stuffed. Giant shells are also often baked, and this is generally possible with the larger pastas like ziti. They won’t fall apart after being in a hot oven for a while. Ravioli and tortellini are stuffed too, and their size is dictated by the same considerations as above, and also how much you’re putting in them.

Additional considerations

Ridges. In general, the larger pastas are good for heartier sauces as I said above. But you can also modify the degree to which sauce sticks to pasta, by choosing between ridged and unridged noodles.

• For example, you might have a bolognese with fine chunks of meat in a thick tomato puree. If you get pasta with ridges, thick sauces will adhere more easily to the outside, as in rigatoni bolognese.

• On the other hand, if the pasta is smooth, it can move more easily in an oil-based sauce. So serve penne with pesto.

How the pasta is cut. Have you ever seen the term “bronze die” on a pasta package before? This means that the dies (machine used for stamping) used to cut the pasta are made out of bronze, as opposed to a more modern material such as Teflon. The result? A rougher cut that, like ridges, holds sauce better.

Open vs. closed shapes. Most of the pasta shapes that come to mind, like wagon wheels, have nowhere for sauce to get trapped. But there are a few shapes, like tiny shells, or campanelle, that allow even a thin sauce to be part of each bite, if that’s what you want.

Curved vs. straight shapes. My best guess on this is that curved shapes are more appropriate for pasta dishes that are meant to be eaten like a casserole. Take macaroni and cheese, for example. I’ve made this with penne a few times, and it just isn’t as satisfying because it becomes somewhat harder to eat - without breaking up the individual pieces, you can’t fit them into your mouth as easily. Curved shapes get the right amount of pasta into a smaller bite.

Whether the pasta cooks uniformly. This is only really an issue for speculative or new pasta shapes, but here’s an interesting article on some attempted pasta redesigns by famous designers.

• One issue that’s brought up by the (very perceptive) author is that these redesigns have points where the pasta has more than one layer - where it intersects with itself.

• In traditional pasta shapes, this double-layering is generally minimized so that the pasta is cooked evenly. Probably not a problem you’ll face with standard pastas.

Wrap up

So, in conclusion, here’s my best guess on how to think about different pasta shapes:

• In general, the bigger the pasta, the heartier / heavier the sauce you can serve it with. Very small shapes go in soup.

• Tubes have the advantage of being able to contain small chunks of tomato, meat, or other flavorful sauce addins. Sort of like impromptu stuffing.

• Strands make sense in smoother sauces, or dishes where something is served alongside the pasta (such as, say, clams).

• You can experiment not only with different sizes of the same pasta, but also with lots of other variables (shapes, ridges, how the pasta is cut) to achieve different culinary experiences.

Lastly, here’s a quick table to talk about what I think are the rationales behind certain famous pasta dishes.

Dish	Description	Possible rationale
Rigatoni bolognese	Rigatoni in a thick, tomato and meat sauce	Rigatoni is a fairly large shape that stands up well to this sauce, while also allowing the sauce to infiltrate the inside of the shape. The ridges provide even more sauce adhesion.
Fettucine alfredo	Fettucine strands in a thick cream and cheese sauce	Thick strands stand up well to the heavy cream sauce; you're eating pasta in a sauce, not the other way around. Using tubes or other shapes wouldn't improve surface area availability.
Linguine alle vongole	Flat, medium width strands served with clams and an olive oil and white wine sauce	Relatively thin strands are able to move around easily in the sauce; since the flavors of the sauce are relatively subtle, the linguine stand up to it just fine. (One thing I'm not sure about is why linguine are used instead of, say, spaghetti. Though note that linguine, being flat, have a higher ratio of volume to surface area.)
Macaroni and cheese	Macaroni, or sometimes other small, tubular pasta, in a cheese sauce	Similar to fettucine alfredo, except that using relatively small, curved tubes allows the resulting dish to be eaten like a casserole.