How do we avoid divide by zero error in a computed column in an SQL server?

To resolve sql server divide by zero, Use IFERROR to suppress the #DIV/0! error. You can also suppress this error by nesting your division operation inside the IFERROR function. Again, using A2/A3, you can use =IFERROR(A2/A3,0).

Or Just add a special case for division by 0:
CREATE TABLE [dbo].[TblDivision] ( [Numerator] int NOT NULL, [Denominator] int NOT NULL, [Result] AS case when Denominator=0 then 0 else (Numerator/ Denominator) end );