If the tiles are well spaced all gaps under 1 4 then you should be able to cover the entire mosaic of 18 x 18 with 2 lbs of grout.
How to grout mosaic tile wall.
The area of the mosaic l x w the thickness of the tiles and the gaps between the tiles.
How much grout you need depends on three things.
To grout wall tiles start by dividing your wall into 3 foot by 3 foot sections so you can work on it before the grout dries.
Grouting is not difficult to do well but it is even easier to do poorly.
Learn my proven system and stop messing around with grout.
Additionally spread the grout into the joints and use the side of your float to compress it.
Grouting is the final step of installing ceramic wall tile after the tile adhesive has fully cured.
When put together over a floor or wall these small tiles contain numerous grout lines which must all be filled to.
Small tiles or mosaic tiles typically measure 2 inches or smaller in size.
The unique layout of mosaic tiles produces many grout lines so grouting is an important step in achieving a clean final look.
Fortunately all you need for a successful grout job is clean water a clean sponge a steady hand and plenty of patience.