The 1L / 100g / 10g Rule
Italian cooks live by one tidy ratio for boiling pasta: one litre of water and ten grams of salt for every hundred grams of dry pasta. So a standard 200 g portion for two people wants 2 litres of water and 20 g of salt; a full 500 g box wants 5 litres and 50 g. The abundant water keeps the pot temperature from crashing when you drop the pasta in, gives long shapes room to move so they do not clump, and dilutes the starch the noodles shed so the water never turns to glue. The 10 g of salt per litre is what the phrase "salty like the sea" actually means, and it is the single biggest difference between bland home pasta and the pasta you remember from a trattoria.
Why Salt by Weight, Not by Pinch
Salting "to taste" fails for pasta water because you are seasoning the noodle from the inside while it cooks, not adjusting a finished dish. The right concentration is what matters, so this calculator works in grams and then converts to teaspoons for you, accounting for the fact that fluffy Diamond Crystal kosher salt takes up far more volume than fine sea salt for the same weight.
Water (L) = pasta_g / 100 x water-factor | Salt (g) = water_L x salt-per-litre
Save a Mug of the Water
The cloudy, salty, starchy water left in the pot is liquid gold. A splash stirred into the pan emulsifies oil or butter with the starch into a glossy sauce that clings to every strand, which is why a cacio e pepe or an aglio e olio comes together with a ladle of pasta water and falls apart without it. Always dip out half a cup before you drain, and never, ever add oil to the boiling water, it only coats the noodles and stops sauce from sticking.
Frequently Asked Questions
How much salt do I put in pasta water?
The classic Italian standard is about 10 grams of salt per litre of water, which works out to roughly one to one and a half teaspoons of fine salt per litre. That gives water that tastes distinctly salty, like seawater, and seasons the pasta as it cooks. Most home cooks dramatically under-salt, which is the main reason their pasta tastes flat next to restaurant pasta.
How much water do I need per 100g of pasta?
The traditional rule is one litre of water per 100 grams of dry pasta, so a 200 g portion for two wants 2 litres and a 500 g box wants 5 litres. You can get away with as little as 7 litres per kilogram in a frugal one-pot approach, but abundant water keeps long shapes from sticking and the pot from cooling when the pasta goes in. Skimping too far makes the water gluey and the pasta clumpy.
Should I add oil to the pasta water?
No. Oil floats on top of the water and does almost nothing while boiling, then coats the drained noodles so your sauce slides right off instead of clinging. The real way to stop pasta from sticking is plenty of water, a good stir in the first minute or two, and not over-draining. Save the oil for the pan, not the pot.
Does salt make pasta water boil faster or slower?
Adding salt actually raises the boiling point very slightly, by a fraction of a degree at these amounts, so technically it boils a hair slower, not faster. The effect is far too small to matter in practice. For that reason it does not matter much whether you salt before or after the water boils, though most cooks add salt once it is boiling so it dissolves instantly and does not pit the bottom of the pot.
Practical Guide for Pasta Water & Salt Calculator
The reason the 1 litre / 100 g / 10 g rule is worth memorizing is that it scales perfectly in your head. Cooking for one with a 100 g nest of pasta? One litre of water, two teaspoons of salt. Feeding a crowd with a whole 500 g box? Five litres and 50 g of salt. Because every number moves together, you never have to re-learn the ratio, you just multiply by how many hundred-gram portions you are making. This calculator does that arithmetic for you and adds a pot-size suggestion so you do not try to fit 5 litres into a 4-quart saucepan.
Salt volume is where most kitchen confusion lives, because not all salt measures the same. Ten grams of fine sea salt is roughly a teaspoon and a half, but ten grams of fluffy Diamond Crystal kosher salt is closer to two and a half teaspoons because the crystals are larger and trap more air. That is why weighing salt is the most reliable method, and why the calculator lets you pick your salt so the teaspoon conversion is right. If you only have one box, just learn the volume for that box and stick with it.
Water volume is the lever most people overlook. Long shapes like spaghetti, bucatini, and linguine genuinely benefit from the generous 12-litres-per-kilo end of the scale because they need length to move freely and not weld together; short shapes and a busy weeknight forgive the frugal 7-litres-per-kilo one-pot approach. The trade-off is concentration: less water with the same salt-per-litre target simply means less total salt to add, while the cloudier, more starch-rich water from a small pot makes an especially silky sauce, which some cooks chase on purpose.
Quick Checklist
- Use about 1 litre of water and 10 g of salt for every 100 g of dry pasta.
- Salt the water until it tastes like the sea, then taste a noodle before draining.
- Bring the water to a full rolling boil before adding salt and pasta.
- Scoop out half a cup of starchy pasta water before draining for the sauce.