I have my own runway 150 yards from the house. It was already a fairly level area in the middle of a blue grass pasture so I didn't have a lot of work to do to turn it into a decent runway. In the early spring after the ground thawed out, and was still mellow, I used a tractor and blade to get rid of the anthills and fill in the cow tracks. There were a few bare dirt patches after I was done with the dirt work, but by the next year the bluegrass had filled in those spots. Through the years I have added a windsock and a steel roof shelter for shade. Now the runway is known as my airport.
The runway is 300' by 75'. I could get by with less width, but probably wouldn't go less than 60' wide. Every plane that I maiden I like to run up and down the runway 10 or 12 times just to get an idea what the ground handling is like and try to shake any screws loose etc. When I am standing at one end of the runway and turning the plane around at the other end of the runway, that is when the 75' is nice as some of my planes have a pretty large turning radius.
I flew mostly 60 sized planes when the runway was first built and on a lot of maiden flights I would use the whole 300' length. On the first few flights the plane may be nose heavy so it will land faster and not flare like it should and I am just not used to the throttle settings that particular plane likes when it lands. Once the plane is dialed in then 200' is plenty. Now I am building 50 and 100cc planes and I think I will add another 50' to the runway. Same thing as the 60 size planes, once I get a plane dialed in 300' is plenty, but the first few flights I wish I had a 350' runway to work with. Another thing I have noticed, if it is calm it always takes more runway than if the wind is blowing. Even a cross wind shortens up the length it takes to land.
In an earlier post you said you would get the transit out. I assume this means you will be doing some major dirt work to get your runway built. If that is the case I would do the dirt work for a bigger runway now, then seed the area you don't think you need back to alfalfa or whatever your hay ground is. When I started flying, I didn't think I would ever be into the size planes that I am now, but it happened. And it will probably happen to you too. If the dirt work is already done it will be easy to make your airport bigger.
Pat