How is CTR calculated?

based on visits or page views?

[uhwebs]

I have a question on how CTR is calculated.
Say I get 1,000 visitors in a day, and 65 clicks. I would say that is 6.5%.

But my Google will say it's like .8%, because I get 8,000 pageviews.

Which is the 'correct' way to calculate CTR? Is it based on visits, or page views?

[webnoob]

by impressions, not visitors.

if you had 8000 ad impressions and 65 clicks then your CTR would be 0.8% so that is correct. 65 / 8000 = 0.8

make it easier:

100 impression, 10 clicks, CTR = 10.0%