Ask ten cooks how much salt goes in pasta water and you will get ten answers, from a pinch to a handful. The truth is that pasta itself has almost no flavour, so the cooking water is the only chance to season it from the inside. Unsalted pasta tastes flat no matter how good the sauce is, while properly salted pasta tastes seasoned even before sauce touches it. This calculator settles the argument: enter your water volume and your salt rate, and it gives exact grams and teaspoons. It works for any pot size, from a small pan for one person to a large pot for a crowd, because the salt always scales with the water.
The standard rate is 10 grams of salt per litre of water, which is about 1.7 teaspoons per litre. A light rate of 7 grams suits cooks who use very salty sauces or who watch their salt intake, and a salty rate of 12 grams suits plain pasta with butter or olive oil, where the pasta carries the dish. For a typical pot with 4 litres of water at the standard rate, you need 40 grams of salt, which is about 6 to 7 teaspoons. That looks like a lot, and it is, but most of it goes down the drain.
That last point surprises people, so it is worth explaining. Pasta absorbs only a small share of the salt in the water; the rest stays in the water you drain away. That is why pasta water needs far more salt than the finished dish would, and why salting the sauce alone cannot fix bland pasta. The salt in the water seasons the pasta as it hydrates, from the outside in, which no later seasoning can reproduce. Think of the water as a brine, not as a finished dish.
Here is a worked example. You are cooking for four people in 4 litres of water. At 10 grams per litre you need 40 grams of salt. If you only have teaspoons, that is 40 divided by 6, about 6.7 teaspoons, so use 7 level teaspoons. Add the salt once the water boils and stir until it dissolves, then add the pasta and stir again so it does not stick. Taste the water before the pasta goes in: it should taste like mild seawater, clearly salty but not harsh.
Salt type changes the measuring, which is why this calculator works in grams first. Fine table salt packs tightly, so a teaspoon weighs about 6 grams, while coarse kosher salt weighs less per teaspoon because of the air between crystals. If you measure by spoon with coarse salt, you will undersalt without realising it. Weighing removes the problem, and if you must use spoons, use level teaspoons and the same salt every time so your results stay consistent.
Two common mistakes are worth avoiding. The first is adding salt to cold water and forgetting it, which is harmless but easy to misjudge. The second is adding oil to the water, which does nothing to stop sticking and makes sauce slide off the pasta instead of clinging to it. Stirring in the first minute does the real anti-stick work, and a large pot with plenty of water gives the pasta room to move. Salt, stir, and skip the oil.
Use this calculator whenever your pot size changes, because the salt must change with the water. A small pot for two needs far less salt than a big pot for a crowd, and guessing the same handful for both guarantees one of them is wrong. Enter the litres, pick your rate, weigh the salt, and the pasta will taste seasoned before the sauce even arrives.