The McArthur Grass (GFDI) and Forest (FFDI) Fire Danger Indices have been used since their development more than 50 years ago. Fire Agencies use the indices to determine Fire Danger Ratings and for tactical planning. Index values as an integer for one or two point locations in a larger area (district) were originally calculated using slide rules. By the 1980’s computer algorithms were developed, resulting in the indices being extended beyond the original scale. The ability to readily produce input values at the scale of 6 or 3km spacing has enabled the Bureau of Meteorology to produce static gridded maps of GFDI and FFDI. These maps highlight the spatial variation of Fire Danger Indices, the variation between Grassland and Forest FDI across the landscape, and also the localised sensitivity of the FDI to the input variables of weather and fuel state. Understanding these spatial variations can assist in the development of improved measures of and communication about fire danger.