Is there a standard measurement that can be used?
The bouillon cubes I am familiar with are equal to 1 teaspoon of powder.
I'd figure it backwards. You need x amount of Bouillon. You can see (from the specific powder AND the specific cubes) how much you'll need of each to make that x amount.
Then calculate the ratio based on those numbers.
Then cook, and discover there's a taste difference, and correct accordingly. :)
The bouillon cubes I use (Wyler's) states on the jar that one cube makes ONE cup of broth. Crushed one to see how it measured up and it came to one teaspoon. Also the reliable sources I've checked all say one cube = 1 teaspoon (tsp). Hope that helps.
I checked the Wyler's website under "tips". They state that one boullion cube = one teaspoon of powder.