Overview
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.
License:
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.
Notes
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.
Arithmetic Operations
Operation  Symbol 

Plus  + 
Divide  / 
Modulo  % 
Times  * 
Power  ** 
Minus   
Boolean Operations
Operation  Symbol 

Boolean And  && 
Boolean Or   
Relational Operations
Operation  Symbol 

Equal to  == 
Greater than  > 
Greater than or Equal to  >= 
Less than  < 
Less than or Equal to  <= 
Not Equal to  != 
Trigonometric Operations
Operation  Symbol 

ACos  ACos(a) 
ACosH  ACosH(a) 
ASin  ASin(a) 
ASinH  ASinH(a) 
ATan  ATan(a) 
ATan2  ATan2(a) 
ATanH  ATanH 
Cos  Cos(a) 
CosH  CosH(a) 
Sin  Sin(a) 
SinH  SinH(a) 
Tan  Tan(a) 
TanH  TanH(a) 
Additional Operations
Operation  Symbol 

Con  Con(a,b,c) 
Is Null  IsNull(a) 
Minimum of two rasters on a perpixel basis  min(a,b) 
Maximum of two rasters on a perpixel basis  max(a,b) 
Set Null  SetNull(a,b) 
Parameters
Parameter name  Description 

Raster Variables  The userdefined variable name and the input raster. 
Expression  Build an algebraic expression to perform spatial analysis on the input raster. 
Cellsize Type  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.

Extent Type  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.