Different brands of basmati rice vary slightly, so it pays to read the package. I usually use Lundberg, which calls for a 1 to 1 1/2 ratio of rice to liquid when cooked on the stovetop. When cooking in the Instant Pot, from which virtually no steam escapes, I reduce the liquid to 1 1/4 cups because I like it slightly softer — you can reduce it to 1 cup if you prefer your rice slightly firmer. If your brand of rice calls for a different liquid ratio, you can use that guidance for stovetop cooking and reduce it proportionally for the Instant Pot.