In the example at left the run is 10.
Roof hip length.
First subtract 1 1 5 inches 2 5 3 8 cm from the width measurement you just took to account for the thickness of the ridge board which will span the length of the roof between the individual rafters.
Then divide this number by 2 to reflect the separate halves of the roof.
Layout is from the center of the first common rafter.
The ridge of a hip roof is equal to the length of the building minus twice the run plus the thickness of the rafter stock.