Tile guy told me he would need 4 bags 50 Lbs each of thinset. Mortar to do a 12x12 bedroom.
isn't that excessive?

Try using this How to Estimate Grout & Thinset for Ceramic Tile | Home Guides | SF Gate A lot depends on the coverage chart on most bags and the size of the tile you are using. Large tiles use deep notched towels. If you only use 3 you can take back the 4th if its unopened.

That seems a bit high but depends on the tile size. You nave 144 sq. ft. 36 tiles per bag. Typically need a 10% cushion. Believe me, it's better to have and not need it than not having it.

Okay thanks a lot.

Thanks