How do US TV ratings work?

[zeebre12]

Thought this may be a better place to stick this than the Pay TV section. When UK TV shows like Coronation Street get- 6.30m (35.4%). This shows the % of people who are watching TV and are watching Coronation Street. What would the % be for some US shows as some of the big shows seem to have low ratings for the size of the country compared to the UK (how many people in total are watching TV)
Like last night for BBC One:
Pointless Celebrities: 5.23m (29.5%)
Strictly Come Dancing: 10.32m (49.2%)
Michael McIntyre's Big Show: 5.74m (26.6%)
Casualty: 3.95m (19.9%)

 

[davideduardo]

Thought this may be a better place to stick this than the Pay TV section. When UK TV shows like Coronation Street get- 6.30m (35.4%). This shows the % of people who are watching TV and are watching Coronation Street. What would the % be for some US shows as some of the big shows seem to have low ratings for the size of the country compared to the UK (how many people in total are watching TV)
Like last night for BBC One:
Pointless Celebrities: 5.23m (29.5%)
Strictly Come Dancing: 10.32m (49.2%)
Michael McIntyre's Big Show: 5.74m (26.6%)
Casualty: 3.95m (19.9%)

Keep in mind that in the US, published reports are based on ratings, not share.

So when we see that "Big Bang Theory" gets a 3.1 rating, meaning it reaches 3.1% of TV homes. But if just 33% of homes are viewing TV at the time the show has a 9.3 share.