This question is an exact duplicate of:
What is the correct verb tense for the phrase "all you need is", when what follows is a plural?
- All you need is paintbrushes and paint.
- All you need are paintbrushes and paint.
Or is neither incorrect? Both forms sound funny to me.
Google shows an order of magnitude more hits for "all you need is two" than "all you need are two", but the latter still has ~500K hits, so it seems that both forms are in common use. (You can also examples of both usages in Google's "News" search.)
Consider a related example:
- All is good.
- All are good.
Both forms are correct, but have slightly different meanings/contexts. The first is correct if "all" refers to "everything" (singular); the second is correct if "all" refers to an implied concrete set of things, as in "all (the widgets) are good". This line of reasoning seems to imply the latter form is correct, since "paintbrushes" are concrete things. (And yet that seems to be the less popular form in common usage, judging by Google hits).