The Imperial system of units is used in the United States.  This system is based on inches and feet, and architectural drawings are generally divided into ‘fourths’ and ‘eighths’.  Most full-sized working drawings are based on the assumption that one inch on paper equals four feet in reality.  I typically use a half-scale when doing preliminary designs of one inch on paper equals eight feet in reality.  This way, a modestly sized house can be sketched out on a piece of letter-sized paper and can easily be sent to clients to review.

(In comparison to metric sizes, the 1/4″ = 1′-0″ would translate as 1:48.  The 1/8″ = 1′-0″ would translate as 1:96.)