square feet to acre measurement

I am looking to purchase a house with at least a half acre of land. Looking at the real estate listings however, they usually will have the land listed as 100 by 100 ft. lot. How do I convert that to a percentage of an acre?
Debora

An acre is 43560 sq ft. That 100' x 100' lot is 10000 sq ft (assuming it has 90 degree corners; weird quadrilaterals could be less).

While not official, there seems to be a smaller "builders acre" that makes allowances for easements, roads, etc. Divide a 100 acre field into 200 lots, they won't be 1/2 acre due to roads, etc, but it will be half a "builder's acre." Ask for the sq footage.

100 X 100 = 10000 sq. ft. One acre is 43560 sq. ft. So devide 10000 by 43560 = .2299568 = approx. 22.9 % or just under a quarter of an acre.

Here's a great site for converting any/all measurements:
http://www.people.virginia.edu/~rmf8a/convert.html

I am looking to purchase a house with at least a half acre of land. Looking at the real estate listings however, they usually will have the land listed as 100 by 100 ft. lot. How do I convert that to a percentage of an acre?
Debora