This is why I like tincture, I can titrate my tincture for the buzz I like. For example if I know I get the buzz I want from 1/2 ml I know I can use 1/2 ml per drink and get the buzz I want. It also gives you the option of having one drink with weed and the other 3 without.
That being said, usually an alcohol extraction is about 75% efficient. So you can estimate potency. For example, if you have 1 gram of 20% THC buds that’s 200mg. The extraction would be 75% efficient so you have about 150 mg in the alcohol. So add a gram of decarbed weed to 30 oz of alcohol to get your desired potency.