A good starting ratio is 1 cup of butter to 7 grams of decarboxylated cannabis. This will give you a moderate-strength cannabutter that’s well-equipped for most recipes. From there, you can go harder or softer per your preferences.
Try 10-12 grams of decarbed weed to a cup of butter if you’re a mad lad or perhaps 3.5 grams if you’re lame. Or go with the standard 1:7 but adjust the dosage in your edible recipes (e.g. halving the required amount of cannabutter for a recipe and replacing it with regular ol’ boring butter.) If you want any further assistance with all the maths and science of edibles, here's a handy tool for calculating the dosage of your edibles.