Help! Which is right?

[2016IsANewYearforMe]

Three is too many.

Or

Three are too many.

Word says the second, but I don't trust it.

Eh? Is, surely!?

Is.

Thank you. It sounded wrong to me too, but I lost confidence when the grammar checker told me it was wrong.

I feel much better now.

The "three" in this case is not referring to three individual things, each of which being "too many" - that doesn't make any sense. In this case the three is a collective noun, which is a single "thing" so to speak.

E.g. "Three are coming today" - each individual one is coming.
...vs... "Three is a crowd" - the one group of three is a crowd.