Indian recipes written abroad often arrive in grams, and American kitchens work in cups. The conversion is where a lot of otherwise good recipes come apart.
Volume measures a container, not an amount
A cup of flour weighs noticeably different amounts depending on whether it was scooped, spooned or shaken level, because packing changes with handling.
The variation is large enough to alter dough hydration, which is the difference between a flatbread that rolls easily and one that cracks at the edges.
Weight has no such ambiguity, which is why bakers and professional kitchens use scales regardless of the country they work in.
Some ingredients are far worse than others
Liquids convert cleanly, since a cup of water is a cup of water. Granulated sugar and rice are reasonably consistent too.
Flours, ground spices, grated coconut and anything sticky are the problem cases, because they compress, clump or cling to the measure.
Ghee and yogurt are worse still, since a cup of either leaves a meaningful amount behind in the vessel it was measured in.
Small quantities amplify the error
A teaspoon of a potent ground spice mismeasured by a third changes a dish audibly, while the same proportional error in the rice would go unnoticed.
Salt varies by crystal size as well, so a teaspoon of coarse kosher salt and a teaspoon of fine table salt are not the same quantity of salt.
This is why recipes increasingly specify which salt they were tested with, and why a substitution there requires adjusting the amount rather than the spoon.
The practical fix in an American kitchen
An inexpensive digital scale removes the whole category of problem and is faster than nested cups, since ingredients can be weighed into one bowl.
Where cups are unavoidable, spooning flour into the cup and leveling with a straight edge gives a far more repeatable result than dipping the cup into the bag.
For fats and dairy, measuring by weight or by displacement in water avoids the residue problem entirely.
Traditional measures were never precise either
Home cooks in India frequently measure by handful, by a particular household cup, or by eye, and the recipes work because they are cooked repeatedly by the same hands.
What carries the accuracy in that system is the cue-based cooking that follows: consistency is corrected during the process rather than at the measuring stage.
A cook using either system successfully is doing the same thing, which is watching the food rather than trusting the number.