The Raster Calculator can do a lot, but the documentation is pretty scarce. I got stuck adding together multiple raster layers with null values in ArcMap. If one of the rasters has a cell with a null value, then when that cell is added to values from other cells it still equals null. null + any value = null The way around this is to use a conditional statement. Con( condition, value if true, value if false ) For example, to check if a cell value is null and reassign that cell value to zero if it is null: Con(isNull("raster_layer"), 0, "raster_layer") So, if you want to sum two raster layers with null values and want to substitute zeros for the nulls, do this: Con(IsNull("raster_layer_1"), 0, "raster_layer_1") + Con(IsNull("raster_layer_2"), 0, "raster_layer_2") This works for ArcGIS Desktop 10.5 and you probably need the Spatial Analyst extension to be able to use the Raster Calculator. You could just us...