I have almost two acres of runoff that would stay mowed and cleared to run into a 1/4 (probably smaller) pond.
Generally speaking, as long as the pond holds water good then is my two acres plus close to two or more acres of runoff from my neighbors land going to be enough runoff area if I build this 1/4 acre or less pond ?

It all depends on the average annual rainfall amounts. In my arid area of Texas, it wouldn't have a chance.

The Dept of Conservation in Mo (at least my agent) told me a 10:1 ratio is what he goes on. I was trying to fill a one acre pond, but only had 8-9 acres of drainage. Unusually wet weather this year has my pond full, but the two previous years were drought years, I was almost 5' down on a one acre pond. (I do have a small leak, and trees right at the water's edge) So keeping it full is not a given.
It's been full, and or running out the overflow pipe off and on since filled in early 2015.

Our expected annual rainfall is around 35".

Mudball, if in the western 2/3 of TN, 4 acres would be just enough to maintain a quarter acre pond about 12 feet deep.

Our rainfall is about 47", I have about one acre of watershed, and my 1/4 acre pond has been over the emergency spillway three times in the 23 months since it was renovated. If I had 4 acres of watershed, I would rarely have a problem with being full, despite the leaks.
My ground above the pond doesn't allow for much soaking in, as it's nearly all clay, and the grass is a little thin.

Thanks for all the great replies.
I believe the type of soil in the area, as well as other factors has a lot to do with the results.
We have a fairly high amount of clay in the surrounding area.
I will keep my fingers crossed.

I have a 1/4 acre wetland with 1/4 acre of watershed. This is the 1st body of water we built 100% ourselves. We used the spoil dirt for a barn pad which is not yet built. We have good clay, cored and packed the berm with a backhoe, and packed the berm in 6" lifts with a sheep's foot roller. It has stayed remarkably full. Once I build the barn and add the roof runoff to the wetland, I am confident it will do very nicely. I really did not expect much, but now understand the value of not cutting corners. We have another pond under construction now and will follow the same recipe for making the dam. This one will have much more watershed (maybe 8 to 1).

Thanks RAH.
Sounds like words of hope.
Glad yours are doing well.