Data Types of Operator Results
Visual Basic determines the result data type of an operation based on the data types of the operands. In some cases this might be a data type with a greater range than that of either operand.
The ranges of the relevant data types, in order from smallest to largest, are as follows:

Boolean — two possible values

Integer, UInteger — 4,294,967,296 (4.2...E+9) possible integral values

Long, ULong — 18,446,744,073,709,551,615 (1.8...E+19) possible integral values

Decimal — 1.5...E+29 possible integral values, maximum range 7.9...E+28 (absolute value)

Single — maximum range 3.4...E+38 (absolute value)

Double — maximum range 1.7...E+308 (absolute value)
For more information on Visual Basic data types, see Data Type Summary (Visual Basic).
If an operand evaluates to Nothing, the Visual Basic arithmetic operators treat it as zero.
Note that the Decimal data type is neither floatingpoint nor integer.
If either operand of a +, –, *, /, or Mod operation is Decimal and the other is not Single or Double, Visual Basic widens the other operand to Decimal. It performs the operation in Decimal, and the result data type is Decimal.
Visual Basic performs most floatingpoint arithmetic in Double, which is the most efficient data type for such operations. However, if one operand is Single and the other is not Double, Visual Basic performs the operation in Single. It widens each operand as necessary to the appropriate data type before the operation, and the result has that data type.
/ and ^ Operators
The / operator is defined only for the Decimal, Single, and Double data types. Visual Basic widens each operand as necessary to the appropriate data type before the operation, and the result has that data type.
The following table shows the result data types for the / operator. Note that this table is symmetric; for a given combination of operand data types, the result data type is the same regardless of the order of the operands.
 Decimal  Single  Double  Any integer type 
Decimal  Decimal  Single  Double  Double 
Single  Single  Single  Double  Double 
Double  Double  Double  Double  Double 
Any integer type  Double  Double  Double  Double 
The ^ operator is defined only for the Double data type. Visual Basic widens each operand as necessary to Double before the operation, and the result data type is always Double.
The result data type of an integer operation depends on the data types of the operands. In general, Visual Basic uses the following policies for determining the result data type:

If both operands of a binary operator have the same data type, the result has that data type. An exception is Boolean, which is forced to Short.

If an unsigned operand participates with a signed operand, the result has a signed type with at least as large a range as either operand.

Otherwise, the result usually has the larger of the two operand data types.
Note that the result data type might not be the same as either operand data type.
Note 

The result data type is not always large enough to hold all possible values resulting from the operation. An OverflowException exception can occur if the value is too large for the result data type. 
Unary + and – Operators
The following table shows the result data types for the two unary operators, + and –.
 Boolean  SByte  Byte  Short  UShort  Integer  UInteger  Long  ULong 
Unary +  Short  SByte  Byte  Short  UShort  Integer  UInteger  Long  ULong 
Unary –  Short  SByte  Short  Short  Integer  Integer  Long  Long  Decimal 
<< and >> Operators
The following table shows the result data types for the two bitshift operators, << and >>. Visual Basic treats each bitshift operator as a unary operator on its left operand (the bit pattern to be shifted).
 Boolean  SByte  Byte  Short  UShort  Integer  UInteger  Long  ULong 
<<, >>  Short  SByte  Byte  Short  UShort  Integer  UInteger  Long  ULong 
If the left operand is Decimal, Single, Double, or String, Visual Basic attempts to convert it to Long before the operation, and the result data type is Long. The right operand (the number of bit positions to shift) must be Integer or a type that widens to Integer.
Binary +, –, *, and Mod Operators
The following table shows the result data types for the binary + and – operators and the * and Mod operators. Note that this table is symmetric; for a given combination of operand data types, the result data type is the same regardless of the order of the operands.
 Boolean  SByte  Byte  Short  UShort  Integer  UInteger  Long  ULong 
Boolean  Short  SByte  Short  Short  Integer  Integer  Long  Long  Decimal 
SByte  SByte  SByte  Short  Short  Integer  Integer  Long  Long  Decimal 
Byte  Short  Short  Byte  Short  UShort  Integer  UInteger  Long  ULong 
Short  Short  Short  Short  Short  Integer  Integer  Long  Long  Decimal 
UShort  Integer  Integer  UShort  Integer  UShort  Integer  UInteger  Long  ULong 
Integer  Integer  Integer  Integer  Integer  Integer  Integer  Long  Long  Decimal 
UInteger  Long  Long  UInteger  Long  UInteger  Long  UInteger  Long  ULong 
Long  Long  Long  Long  Long  Long  Long  Long  Long  Decimal 
ULong  Decimal  Decimal  ULong  Decimal  ULong  Decimal  ULong  Decimal  ULong 
\ Operator
The following table shows the result data types for the \ operator. Note that this table is symmetric; for a given combination of operand data types, the result data type is the same regardless of the order of the operands.
 Boolean  SByte  Byte  Short  UShort  Integer  UInteger  Long  ULong 
Boolean  Short  SByte  Short  Short  Integer  Integer  Long  Long  Long 
SByte  SByte  SByte  Short  Short  Integer  Integer  Long  Long  Long 
Byte  Short  Short  Byte  Short  UShort  Integer  UInteger  Long  ULong 
Short  Short  Short  Short  Short  Integer  Integer  Long  Long  Long 
UShort  Integer  Integer  UShort  Integer  UShort  Integer  UInteger  Long  ULong 
Integer  Integer  Integer  Integer  Integer  Integer  Integer  Long  Long  Long 
UInteger  Long  Long  UInteger  Long  UInteger  Long  UInteger  Long  ULong 
Long  Long  Long  Long  Long  Long  Long  Long  Long  Long 
ULong  Long  Long  ULong  Long  ULong  Long  ULong  Long  ULong 
If either operand of the \ operator is Decimal, Single, or Double, Visual Basic attempts to convert it to Long before the operation, and the result data type is Long.
The result data type of a relational operation (=, <>, <, >, <=, >=) is always BooleanBoolean Data Type (Visual Basic). The same is true for logical operations (And, AndAlso, Not, Or, OrElse, Xor) on Boolean operands.
The result data type of a bitwise logical operation depends on the data types of the operands. Note that AndAlso and OrElse are defined only for Boolean, and Visual Basic converts each operand as necessary to Boolean before performing the operation.
=, <>, <, >, <=, and >= Operators
If both operands are Boolean, Visual Basic considers True to be less than False. If a numeric type is compared with a String, Visual Basic attempts to convert the String to Double before the operation. A Char or Date operand can be compared only with another operand of the same data type. The result data type is always Boolean.
Bitwise Not Operator
The following table shows the result data types for the bitwise Not operator.
 Boolean  SByte  Byte  Short  UShort  Integer  UInteger  Long  ULong 
Not  Boolean  SByte  Byte  Short  UShort  Integer  UInteger  Long  ULong 
If the operand is Decimal, Single, Double, or String, Visual Basic attempts to convert it to Long before the operation, and the result data type is Long.
Bitwise And, Or, and Xor Operators
The following table shows the result data types for the bitwise And, Or, and Xor operators. Note that this table is symmetric; for a given combination of operand data types, the result data type is the same regardless of the order of the operands.
 Boolean  SByte  Byte  Short  UShort  Integer  UInteger  Long  ULong 
Boolean  Boolean  SByte  Short  Short  Integer  Integer  Long  Long  Long 
SByte  SByte  SByte  Short  Short  Integer  Integer  Long  Long  Long 
Byte  Short  Short  Byte  Short  UShort  Integer  UInteger  Long  ULong 
Short  Short  Short  Short  Short  Integer  Integer  Long  Long  Long 
UShort  Integer  Integer  UShort  Integer  UShort  Integer  UInteger  Long  ULong 
Integer  Integer  Integer  Integer  Integer  Integer  Integer  Long  Long  Long 
UInteger  Long  Long  UInteger  Long  UInteger  Long  UInteger  Long  ULong 
Long  Long  Long  Long  Long  Long  Long  Long  Long  Long 
ULong  Long  Long  ULong  Long  ULong  Long  ULong  Long  ULong 
If an operand is Decimal, Single, Double, or String, Visual Basic attempts to convert it to Long before the operation, and the result data type is the same as if that operand had already been Long.
The & operator is defined only for concatenation of String operands. Visual Basic converts each operand as necessary to String before the operation, and the result data type is always String. For the purposes of the & operator, all conversions to String are considered to be widening, even if Option Strict is On.
The Is and IsNot operators require both operands to be of a reference type. The TypeOf...Is expression requires the first operand to be of a reference type and the second operand to be the name of a data type. In all these cases the result data type is Boolean.
The Like operator is defined only for pattern matching of String operands. Visual Basic attempts to convert each operand as necessary to String before the operation. The result data type is always Boolean.
Reference
Data Type Summary (Visual Basic)Operator Precedence in Visual Basic
Operators Listed by Functionality
Arithmetic Operators (Visual Basic)
Comparison Operators (Visual Basic)
Option Strict Statement
Concepts
Operators and Expressions in Visual BasicArithmetic Operators in Visual Basic
Comparison Operators in Visual Basic