Step 1: Calculate the Size of the Leaf Index Row

Calculating of the size of nonclustered index rows depends on whether the keys are fixed- or variable-length. Use the first formula if all of the keys are fixed-length. Use the second formula if keys include variable-length columns.

Calculate the size of nonclustered leaf rows with fixed-length keys only:

7 + (Sum of fixed-length keys) = Size of leaf index row

Calculate the size of nonclustered leaf rows with variable-length keys:

9 + (Sum of length of fixed-length keys) + (Sum of length of variable-length keys) (Number of variable-length keys) + 1 = Subtotal

(Subtotal) + ((Subtotal / 256) + 1) = (Size of leaf index row)

The values 7 and 9 in the previous equations are overhead that SQL Server uses for internal storage.