Al dente cooking is a transitional state that lasts for a very short amount of time (one minute longer in boiling water makes pasta too soft, one minute shorter and it's still crunchy). For this reason, authentic Italian pasta packages state a precise cooking time, which is very reliable to make a good al dente pasta.
A cooking time interval (e.g. "7 to 10 minutes") is usually given to accommodate to other countries taste, who may prefer a softer pasta, and therefore its presence could be a good indicator of an Italian look-alike pasta brand. In this case the lower figure indicates the al dente cooking.
Lacking this information, a good cooking time can be figured by cross section size, length and shape of pasta: obviously, thicker and squat formats require more time. Complex shapes, such as farfalle, can be trickier because a thick core could reach the al dente cooking while the thinner edges are already too soft.
As a rule of thumb, cooking times for common pasta formats are:
- Long and very thin (spaghettini, bavette): 6 min
- Long and thin (spaghetti, linguine, bucatini): 8 min
- Short and thick (maccheroni, rigatoni, fusilli): 12 min
- Small and thick (farfalle) : 8 min
- Small and thin (pasta usually boiled straight into broth): 6 min
These cooking times apply only for dry durum-wheat pasta; other types (such as fresh egg pasta) usually have a shorter cooking time.
After straining the boiling water, pasta continues to cook by its own heat; for this reason it has to be eaten as soon as possible. Only for some Italian regional recipes (typically pasta boiled straight into a thick vegetable juice, e.g. pasta with beans, pasta with potatoes) you may want to let it rest for up to 5 minutes after straining to let the juices coagulate.
Also, for recipes where pasta has to undergo a second cooking after boiling (e.g. stir frying in a pan with vegetables, shrimps, mushrooms, etc.) a better result is obtained by boiling pasta just one minute less than the cooking time given on the package.
You need 1.1x as much water as pasta for al dente! I measured this myself, cooking penne rigate (in water, not sauce) - 200g of pasta weighed 420g after being cooked and thoroughly drained.
The estimate below from the nutrition facts is 1.4x, which probably corresponds to typical American overcooked pasta - a surprisingly large difference from mine. I'm guessing you'll be somewhere between, maybe 1.25x.
You can also ballpark it from nutrition facts. Cooked spaghetti has 31g carbs per 100g pasta, and dry spaghetti has 75g carbs per 100g pasta. So 100g dry pasta turns into 100g*75/31 = 242g of cooked pasta, meaning the added water was ~1.4x the weight of the pasta. So for a pound of pasta, that's 1.4 pounds or about 2 2/3 cups of water. Given people's tastes, this might be a little past al dente, so I would personally start with maybe 1.25 cups of water then add a little more if necessary. (I'll also try cooking pasta normally and weighing it if I get a chance.)
Note: if you have a significantly different variety of pasta, it will obviously behave differently. This is for pasta that's 13% protein and 75% carbohydrates. For the standard 2oz/56g (dry) serving on the package, it'll say 7g protein and 41-42g carbohydrates. I checked Barilla, De Cecco, Ronzonni, Garofalo, Safeway store brand, Trader Joe's store brand, and those nutrition facts, and they all matched. If you're branching out to other styles like whole grains or egg noodles, things will obviously change, but things are very uniform in the US.
Best Answer
Adding your pasta to cold water before boiling it may help. You will need to stir more often overall, but the shells won't initially stick together as soon as you add them to the water, and then you can stir to prevent the sticking as they become softer.
Harold McGee in a New York Times column wrote this:
What happens is that the starch on the noodles gets rinsed off in the water before it can gelatinize and stick to everything. So you will have to stir even before the water gets warm.