How Warp works
The Warp tool first determines the extent of the output warped raster and sets the number of rows and columns to be about the same as in the input raster. Some minor differences may be due to the changed proportion between the output raster's sizes in the x and y directions. The default cell size used will be computed by dividing the extent by the previously determined number of rows and columns. The value of the cell size will be used by the resampling algorithm.
Below is an example of the most common two-dimensional coordinate transformations: