150 grams of raw white rice to cups

Raw white rice converts more cleanly than most pantry staples, but the cleanliness is deceptive. Each grain is a hard, polished ellipsoid roughly 6 to 7 millimeters long for long-grain varieties, and those ellipsoids do not tessellate. They pack with substantial void space between them, and the size of those voids depends entirely on how the grains settle. A cup scooped straight from the bag traps more air than a cup poured slowly and tapped down, and the difference between the two can run six or seven percent. The grains themselves are mostly starch with the bran and germ stripped away, so moisture content is low and stable (around 12 percent), which means the grain-to-grain density is consistent batch to batch; the variability lives entirely in the packing, not the kernel. USDA FoodData Central pegs raw long-grain white rice at 0.7819 g/ml, or 185 grams per US cup, and that figure assumes a relaxed pour, not a packed measure.

The single most common mistake is conflating raw and cooked rice in a recipe conversion. White rice roughly triples in volume and weight when cooked because each grain absorbs about two parts water for every part rice. A recipe that calls for "1 cup rice" almost always means raw, and a recipe that calls for "1 cup cooked rice" means something entirely different (closer to 60 grams of dry rice, not 185). People scaling rice dishes up or down, or trying to hit a specific cooked yield from a weight measurement, routinely triple their rice or end up with a third of what they wanted. If you are not sure which the recipe means, the surrounding context tells you: raw rice gets a water ratio and a cook time, cooked rice gets folded into something or fluffed.

To measure raw white rice correctly, scoop with a dry cup measure directly into the bag or canister, then level the top with the back of a knife or a straight edge. Do not tap, shake, or press the cup against the side of the container, all of which compress the grains and add 5 to 10 grams. If you are weighing instead (and for rice you should), tare a bowl on a digital scale and pour until you hit 185 grams per intended cup. Weighing is faster and bypasses the packing problem entirely, which matters more for rice than for flour because the absorbed water in the cooking step amplifies any starting error: 10 grams extra rice means 20 extra grams of water absorbed and a noticeably wetter or drier pot.

Density matters most for stovetop and rice cooker preparation, where the rice-to-water ratio is the entire recipe. Long-grain white rice classically wants 1.5 to 1.75 parts water by volume to 1 part rice, and that ratio assumes the rice cup is measured the same way every time. If you scoop heavy on a Tuesday and light on a Thursday using the same water amount, you get gummy rice one day and crunchy rice the next. Pilafs, paellas, biryanis, and rice pudding are equally sensitive because the liquid is calibrated to a specific dry quantity that has to fully hydrate. Sushi rice (a different variety, but the principle holds) is the most punishing of all; the texture window is narrow and a packing error of a few percent shows up as visibly mushy or visibly hard grains. Soups and stir-fries that use already-cooked rice are forgiving by comparison.

For substitution, jasmine rice and basmati rice convert at nearly identical densities (within 2 percent of long-grain white) and can be swapped gram-for-gram without recalculating, though cooking ratios shift slightly: jasmine wants a touch less water, basmati wants a soak. Brown rice is denser per cup (the bran adds weight) and needs more water and longer cooking, so a one-to-one substitution by volume gives you under-hydrated brown rice. Parboiled (converted) rice runs close to raw white in density but resists overcooking, making it a reasonable swap when timing is unreliable.