The strategic placing of commercials plays a vital part in a sitcom's timing. Indeed, The Scriptwriter's Network website suggests that sitcoms are written in view of advertisements and that breaks must be placed in the right spot for the advertisers to put up their wares.
Sitcoms with a viewing slot of one hour tend to run for 45 minutes, excluding commercials. The Stage website cites title sequences and "other elements" as aspects that encroach upon the allocated 60- or 30-minute sitcom slots.
According to the Script Frenzy website, two pages of a sitcom script tend to average one minute of screen time. This is due to the fact that the sitcom script format is dependent upon double spacing.