To calculate the grams from a recipe given in cups, it's vitally important to consider what the ingredient is. A cup of ball-bearings will weigh much more than a cup of feathers .
 Therefore, there's no single gram equivalent for a cup; salt can be as heavy as 300g, while fresh breadcrumbs would only come to 60g. It all comes down to the density of the ingredient.

How to convert grams to cups  

To convert a gram measurement to a cup measurement, divide the weight by 236.588236 times the density of the ingredient or material. Thus, the weight in cups is equal to the grams divided by 236.588236 times the density of the ingredient or material.

To save time, you could use conversion online tools:

https://www.calculatorful.com/grams-to-cups