Oracle Index Sizing Question

This is based on an 'Analyze Table(or Index) Compute Statistics' script already having been run.

Is there a more simplified way of sizing Oracle indexes to get a general estimate than following the 'Calculating Space for Indexes' in the Oracle7 Server Administrators Guide?

In sizing tables, I multiply num_rows*avg_row_len from user_tables to get a general estimate.

Any answer appreciated!

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