Map Algebra is a way to perform spatial analysis by creating expressions using algebraic operators. With the Calculator function, you can create and run expressions and incorporate them into function chains.
The following operators are available with all license levels: plus, minus, times, divide, and power. All other operations require either the ArcGIS Image Analyst extension or the ArcGIS Spatial Analyst extension.
This function provides access to all existing math functions so you can make calls to them when building your expressions. To assist you, autocomplete is built in to provide access to the operators as well as the math functions.
The available operators are listed in the table below.
Greater than or Equal to
Less than or Equal to
Not Equal to
Minimum of two rasters on a per-pixel basis
Maximum of two rasters on a per-pixel basis
The user-defined variable name and the input raster.
Build an algebraic expression to perform spatial analysis on the input raster.
Choose which cell size to use in the output raster. If all the input cell sizes are the same, all the options will yield the same results.
Choose which extent should be used in the output raster:
Examples of expressions
Expressions can be a simple one line of code, or it can be a several lines of code.
Simple Conditional Statement
Find elevation values above 4,000 feet. Give these areas a value of 1 and all other areas a value of 0.
Nested Conditional Statement
Find areas where slope is below 10 degrees and NDVI is above 0.5. Give these areas a value of 1. For all other areas, assign a value of 2 if slope is above 10 degrees and elevation is over 2,500 feet. All other areas are assigned a value of 3.