Got different cell sizes from a rasterised data

Pls can anyone help me find where my proceeding went wrong during the process of rasterizing the Land cover data of Nigeria which was obtained from FAO database. During the process of rasterizing the land cover data, I used the following information which gave different cell sizes between the input cell size and output size (measured).

From polygon to raster, I employed; **Input feature: selected land cover data layer (nga_gc_adg) **Value field: GRODCODE **Output raster dataset: H:\Arcgis\defaul.gdb\nga_gc_adg_polygonTo raster1 **Cell assignment type: CELL CENTRE **Priority field (optional): None **Cell size (optional):0.038.

The question is that instead of the same 0.038km used as the cell size, when I measured the smallest cell size of the rasterized data, I got much higher cell size (4.24km)compared to the input cell size (0.038km). Kindly assist me identify the mistake or the cause of this disparities occurred in cell size.