An Indian recipe rendered into US cups and teaspoons often produces something slightly off. The conversion loses information because the original was not written in a measuring system at all.
The source measurements are not volumetric
Indian home cooking traditionally specifies weight for staples and approximations for everything else: a katori of dal, a fistful of rice, a lemon-sized ball of dough. These reference the cook's own equipment and hands.
Weight is exact and travels perfectly. The approximations do not, because a katori is whatever small steel bowl that kitchen owns and a handful depends on whose hand it is.
Converting them requires someone to decide what the original meant, and that decision is invisible in the finished recipe. The reader inherits a precise-looking number that was a guess.
Volume betrays anything that packs
Flours, ground spices and lentils compress. A cup of atta scooped straight from the bag holds substantially more than a cup spooned in loosely, and neither method is stated in most recipes.
For a bread dough where the flour-to-water ratio decides everything, that variation is the difference between dough that handles well and dough that tears. Weight removes the problem entirely.
Indian grocery flours also differ in absorption from American all-purpose flour, so even a correct volume conversion can need a different amount of water on the day.
Spice quantities carry a hidden variable
A teaspoon of chili powder means nothing without knowing which chili powder. Indian varieties range from mild and deeply colored to genuinely fierce, and American chili powder is usually a spice blend containing cumin and oregano.
The same problem applies to garam masala, which is a family of blends rather than one product. A recipe's quantity was calibrated to whatever the writer's household used.
Some units resist conversion completely
Instructions like cooking until the oil separates, or until the mixture leaves the sides of the pan, are measurements of state rather than time or volume. They are more reliable than any number.
Recipes rewritten for an American audience often replace those cues with minute counts, which fail as soon as the pan, the burner or the batch size changes.
What actually transfers
A kitchen scale removes most of the loss for anything dry. Weighing flour, rice and lentils makes an Indian recipe behave consistently regardless of how it was written.
For everything else, treating stated quantities as a starting ratio and adjusting by taste is closer to the original method than following the numbers precisely. The recipes assume the cook is tasting.