If/Then Formula Question

You should be using VLOOKUP rather than IF statements.

Create a table somewhere in your workbook containing the Material and weight cost (make sure its in alphabetical order). Then give the table a name (Ive used "Materials" in the example).

Then use VLOOKUP as per the example below

Assuming you enter the code in A1, the Weight in B1 and have the answer in C1 then enter the following in C1

=VLOOKUP(A1,materials,2,FALSE)*B1

More on VLOOKUP > https://support.office.com/en-gb/art...8-93a18ad188a1