It can just be a schluter edge at the tile and the carpet gets rolled. Or a white marble threshold, or? Can you show your selections?

Sorry -- I am not computer literate enough to do that! What color schluter and would it be metal? Can you just buy a whote marble threshold easily or are they custom-made? Thank you for helping.

white marble...

Yes, you can buy white marble thresholds easily. They are commonly used. I think Schluter would be more appropriate if the style of the rooms is contemporary.

Why that carpet and why that tile?

Why do you want a white marble threshold at the break between two perhaps!! Not complementary flooring?

What IS the "beige" carpet?

This is the tile?

Take a tile to the Schluter samples .........for exact color and finish . Probably a brushed stainless.

Agree with Hallett, roll the carpet over the tile

No not over the tile, that creates a trip hazard and gets dirty. Roll it AT the tile so they are essentially flush. Yes a color matched schluter just to create an edge, it’s not a detail to draw attention to

I have a piece of synthetic marble as transition piece for upstairs carpeted hallway into our bathrooms.

How does white marble come into play with this already mismatched flooring choice as invisible as possible would be the anwser for the transition so proably schluter . The tile for the bathroom floor is a bit confusing it loks like a large tile to look like small tiles why??? Usually gray and beige are not great together but I would need to see the tile and carpet together to choose color for the schluter

We have a carpet-to-tile situation in our kids' area upstairs, and here's how it was done. The carpet just meets with the tile. From the bathroom angle, you can see where the carpet pad stops so the materials meet flush.