Siding length, siding width and exposure need to be entered in inches and in decimal format.

Ex: Most commonly used board. 12' x 8 1/4" with an exposure of 7"
Values that need to be entered for this size board would be

Siding Length: 144" 
Siding Width:  8.25
Exposure:  7

For wall length enter the total length of your wall in decimal format feet. For roof pitch enter the number your roof rises in 12" Fraction To Decimal Conversion Chart

1/8     0.125 
1/4     0.25
3/8     0.375
1/2     0.5
5/8     0.625
3/4     0.75
7/8     0.875

The amount given of total siding needed does not include a waste factor.