Layout is from the center of the first common rafter.
Roof hip length.
For many people being able to get the right kind of hip roof calculator is very important as knowing how to measure a hip roof is going to be vital to making sure that it turns out well.
In the example at left the run is 10.
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.