What classifies a house a mansion?

Question

is there a specific amount of square feet or something?

Answer 1

Answer above is pretty accurate. Same as If you took a Home out of a gated community with your neighbors only feet away and moved that house on a few acres, that would look like a mansion.

Answer 2

The term "mansion" is not a term used in real estate.

To people that live in a 3rd world country, everyone in the US lives in mansions.

To someone that lives in a $50K shack, he may see a $400K home as a mansion...and that same guy may only see a home at $1.0 million as one.

It's subjective.