Well mushrooms you can measure the weight of the dry amount and dose according to that, granted there are hundreds of different cubensis strains that have different potency, and highs. Best to go on word of mouth with both acid and mushrooms, but shrooms are generally calculated easier.
Ie - with acid your friend that trips all the time is like "Man I took 3 hits of that stuff and I was GONE" meaning you should likely take 1 or a half and feel it out before committing. Then again acid affects everyone differently, set, setting, mood, sleep, health, etc can all be factors in how it affects someone.
WHile with mushrooms, unless you have like a super strength strain like Puerto Ricans or something (which you likely would've been told and paid a lil extra for), you can go by grams. Like 1 gram, meh. 2.5 decent mild to intense, but not to lengthy. 3.5-4.5 - Good trip. 5 grams + and you're going to Andromeda or somewhere close by.