Rice seems simple until it is not. Too much water and you get porridge; too little and the centre stays hard while the bottom burns. The problem is that different rice types need very different amounts of water, and a recipe that works for white rice fails for brown rice or wild rice. This calculator fixes that: pick your rice type and your servings, and it gives the dry rice weight, the water volume, and the ratio behind both numbers. Once you know your ratio, cooking rice becomes a repeatable routine instead of a fresh guess every night.
The serving size is the starting point. One serving is 75 grams of dry rice, which cooks to roughly 200 grams, a sensible portion for most adults. Four servings therefore need 300 grams of dry rice. The water is that weight times the ratio for the type: white rice at 1.5 times needs 450 millilitres, brown rice at 2 times needs 600 millilitres, basmati at 1.5 times needs 450, jasmine at 1.25 times needs 375, wild rice at 3 times needs 900, and sushi rice at 1.2 times needs 360.
Why do the ratios differ so much? It comes down to the grain. White rice has its bran removed, so water reaches the starch quickly and less water is needed. Brown rice keeps its bran, which slows absorption and needs more water and more time. Wild rice is not true rice at all but a grass seed with a tough coat, which is why it needs three times its weight in water and a long cook. Jasmine and sushi rice are shorter grains that need a little less water to stay separate or sticky as intended.
Here is a worked example. You are cooking basmati for four people. Four servings are 300 grams of dry rice, and at a ratio of 1.5 the water is 450 millilitres. Rinse the rice until the water runs mostly clear, which removes surface starch and stops clumping, then add the measured water, bring it to a boil, cover with a tight lid, and turn the heat to the lowest setting. Cook for about 12 minutes, then rest off the heat for 10 minutes before fluffing with a fork.
The lid and the rest matter as much as the ratio. Lifting the lid lets steam escape, which is water leaving the pot, so a pot that is opened often effectively cooks with less water than you measured. Stirring breaks grains and releases starch, which turns separate rice into a sticky mass. The rest after cooking lets moisture spread evenly through the pot, so the top grains, which cook in steam, finish as evenly as the bottom grains, which cook in water.
Brown and wild rice need patience beyond the ratio. Brown rice typically takes 40 to 45 minutes, and wild rice can take 50 to 60 minutes, compared with 12 to 15 minutes for white rice. Do not rush them with high heat, which burns the bottom before the centre softens. If the rice is still firm when the water is gone, add a splash of hot water, cover again, and give it ten more minutes rather than starting over.
Use this calculator as your base, then adjust once for your pot and your stove. A wide pot loses more steam than a narrow one, and a loose lid loses more than a tight one, so if your rice is consistently dry, add a small extra splash next time and note it. Once you find the adjustment that works in your kitchen, the same ratio will give the same result every time, and rice stops being a gamble.