Where to? Mostly, what I laid out already.
OneDrive works for other types of files which do not require the type of sharing that Access accdbs require. (As mentioned, there are several good articles around the internet on the technical reasons.) You are using it as a single user? Put it on the local computer. If you need to use it on different computers at different locations, you could put a copy in OneDrive to download at those other locations, but running it should always be done locally to make life less hassle.
You call it a "calculator", which implies storing data is not the main focus.