Not sure what about you but i used to struggle in converting cooking units, from a recipe that has 125 gram of flour..and i use cups... so, it was always a wild guess till i found this very handy, useful and right to the point website: Online Units Converter (Cooking Ingredients Conversion)
Hope this would help you as much as it helps me!
In the example you gave, 125 grams to be converted to cups, ou have to know to choose the ounces category for volume and not the ounces category for weight. 125 grams is a weight measure that converts to 4.4 ounces of weight but 1 cup in fluid ounces.
"If you want to make an apple pie from scratch, you must first create the universe." -Carl Sagan
Many of the recipes I get to test drive have some of the ingredients in cups and others by weight. I weigh all the ingredients because that is the information that the person who does the ordering needs. For example, last week's recipe required 1 c farro (uncooked). When weighed, it was 200 g, 1/2 c almonds and cashew = 75 g. The same recipe required 400 ml of diced tomatoes. When I start prepping, the first thing that comes out is my scale set to grams.