On the other treads, from riser to riser horizontally is 10". And there is about 1" of nose hanging off the front. So to cover that, I'd need an 11" wide tread. I had a 10" board. So I split the difference - my repair tread has 1/2" nose hanging out over the front riser (this is not clearly seen in my picture) and the rear of it is 1/2" in front of the rear riser. OK, to be perfectly honest, I did not install a riser at the front of my replacement tread. My "riser" is made of, ahem, carpeting that is nailed down in place. So technically my tread "has 1/2" nose in front of where the riser should be".Aside from the lack of toe kick and bullnose edge no one would ever tell you fixed it. I suspect the step you fixed may be stronger than the original.