No, you're not...but you cannot compute the amount of fencing needed from the area. Lots with the same area and different shapes can have different boundary lengths. I can tell you that if your property is a rectangle you will need at least 1866 feet of fencing, but if it was very long and narrow (a "spaghetti farm") you might need a great deal more. The absolute minimum for any shape would be a circle; you would need only about 1650 feet. But circular lots are rare.

If you're getting it done commercially the contractor will compute it for you as part of the estimate (but you might want a figure yourself, to double check.). If you're doing it yourself you will need to measure the boundary. This could be done by pacing it off. Or you could use a long tape measure, a trundle wheel, or a 100' cord with knots every ten feet. A GPS would work too.

As most of these methods are somewhat inaccurate, then either allow an extra fifty feet when you buy, or be prepared to go back for another small load of fence.

Good Hunting!
RD