The Noahic Flood deposited and emplaced a significant amount of sedimentary and volcanic rock on the continents. Much of it remains despite appreciable Recessional Stage erosion. How much? We answer using a method in Colorado as a pilot for many other locations. The principle is simple: creating grids of the basal and upper diluvial boundaries, then subtracting the lower from the upper. In Colorado, we chose the top of the Precambrian crystalline surface as our basal boundary and digitized a Colorado Geological Survey map into a Geographic Information System (GIS). NOAA’s ETOPO1 Digital Elevation Model (DEM) of surface topography was selected as the upper boundary. Small volumes of Precambrian sedimentary and metasedimentary rocks and most of the San Juan and Thirty-Nine Mile volcanic fields were not included in the final calculation, and minor postdiluvial sediments were ignored. The total Flood rock record in Colorado totals more than onehalf million cubic kilometers, predominantly in six sedimentary basins. Our method allows recalculation for revised or alternate boundaries.