How do I combine the values of cells for 3 rasters for cells where they overlap. I want the output raster to cover only the area of the overlap for the 3 rasters and the output cell values to be a sum of the values of the 3 original rasters.

I am using arcmap 10.2. If this is possible through raster calculator it will be preferable. Or any of the spatial analyst tools

2 Answers 2


Raster Calculator can do this -- indeed, the example illustration on the help page shows exactly what you want to do. The resulting raster will only cover the overlap area, which I often find problematic for my analyses but sounds like what you need.

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Other options would work but are more complex than you need. The Plus tool only adds two rasters at a time and would involve running the tool twice. The Weighted Sum tool could work if you assign a weight of 1 to all the rasters. I'd just stick with Raster Calculator.

  • Thank you all. What about nodata, I hope nodata values are ignored in the calculation? Dec 1, 2014 at 17:51
  • Yes, NoData is ignored.
    – Erica
    Dec 1, 2014 at 18:41

The tool to do this is called cell statistics

Select the option SUM

In the environments setting (Output Extent) set the output extent to intersect

  • Yes, I'd forgotten about Cell Statistics :)
    – Erica
    Dec 1, 2014 at 18:41

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