Glazed ceramic tiles will always have a small variation in size from tile to tile in each batch. This is due to the fact that they are made from natural clay and silicas and then fired at high temperatures. During the manufacturing process, the tiles shrink to their finished size. Before being packed, tiles are sorted for colour (tonality) and size (calibration) based on certain accepted industry standards.
Glazed tiles are laid with spaces or grouted joints between them and so this variation is taken up in these grout joints.
Vitrified, porcelain, or full bodied tiles are 'rectified' in the factory. After firing, these unglazed tiles are fed through a machine that actually cuts or grinds the tiles to size. These tiles have very small tolerances in size variation. Of course, from time to time, a malfunction in the sorting process may allow tiles to be packed with an overly generous variation in size.
Tiles shrink during manufacture, and that shrinkage can vary from tile to tile. The industry standards, Asian, Australian and European, ensure that the variation is kept to an acceptable level.
For example, a tile 300mm x 300mm is allowed to vary in size up to 2.25mm either side of the work surface. This means that the tiles can be 297.75mm to 302.25mm and still be within the standard.
Your tiler will soon tell you if the tiles vary in size by too much. To satisfy your curiosity, you can lay a box full of tiles of the floor and see for yourself how the size variation can be taken up.
If you still think that your delivery of tiles has too much variation in size, take a box back The branch will check the variation, and also, call through to the warehouse to see if that variation is indicative of the rest of the stock.
If we have stock that is more dimensionally accurate, we can then arrange to swap your order for a new one.
If that is not acceptable, the only other option is to reselect your tiles.
Whatever the situation, the tiler should not lay the tiles if the variation is too great, or if you are not going to be happy with the finished job. We can't be held responsible once the tiles are laid.