Index rows containing variablelength columns require more overhead than index rows containing only fixedlength values.
Use this formula if the index contains only fixedlength keys and are defined as NOT NULL:
Formula 


7 
(Overhead) 

+ 
Sum of fixedlength keys 

= Size of leaf index row 
Use this formula if the index contains any variablelength keys or columns defined as NULL:
Formula 
Example 


9 
(Overhead) 
9 

+ 
Sum of length of fixedlength keys 
+ 
4 

+ 
Sum of length of variablelength keys 
+ 
20 

+ 
Number of variablelength keys + 1 
+ 
2 

= Subtotal 
35 



+ 
(Subtotal / 256) + 1 (overhead) 
+ 
1 

= Size of leaf index row 
36 