Hi,
How many poles do you need to fence a 3 acre area?

How far apart do you plan to install your poles and what materials are you using?

It all depends how far a apart you want them and what animlas the fence is going to keep in.

Space 8' apart right at 108 per perfectly square acre.

More like 208 for this piece of land. We still have not heard the spacing. This porperty has approximately 1670' of perimeter.

I intend to span the posts 7' apart on the 3 acre plot.

1670 divided by 7 minus 1 should give you a accurate pole count not taking into account any gate.

3 acres is approx. 130680 ft2 which is approx. 1452 ft perimeter.
1452 divided by 7 minus 1 is equal to 206 poles not taking into account any gates.

Not sure where you got 1452, the perimeter of 3 acres is 1669.6 '