If you are converting a numeric expression to a NUMERIC data type and the value is too big for the storage size, you will get an arithmetic overflow error as shown in the following examples:

-- Overflow error on implicit conversion

DECLARE @x FLOAT(24);

DECLARE @y NUMERIC(5,2);

SET @x = 12345.12E+00;

SET @y = @x;

GO

Msg 8115, Level 16, State 6, Line 4

Arithmetic overflow error converting real to data type

numeric.

-- Overflow error on explicit conversions

DECLARE @x FLOAT(24);

SET @x = 12345.12E+00;

SELECT CAST(@x AS NUMERIC(5,2));

SELECT CONVERT(NUMERIC(5,2),@x);

GO

Msg 8115, Level 16, State 6, Line 3

Arithmetic overflow error converting real to data type

numeric.

Msg 8115, Level 16, State 6, Line 4

Arithmetic overflow error converting real to data type

numeric.