Gdal offers many useful tools which I use in a daily basis including things like gdal_calc.

In a windows environment, after installing gdal through OSGeo4W, opening the OSGeo4W Shell and typing o-help lists the tools available.

Installing a recent release of osgeo4w, I found that I could no longer find or run gdal_calc. After reading around, I found it again by running py3_env in the osgeo4w shell. This sets up the shell for python 3.

Searching for gdal_calc using where gdal_calc could then locate gdal_calc again and all was well :)

You can also use Python 3 through the shell now by typing python3.