In his book "The God Delusion", Richard Dawkins devised a seven-point belief scale. Here's a summary of each point.
1. Strong Theist: I do not question the existence of God, I KNOW he exists.
2. De-facto Theist: I cannot know for certain but I strongly believe in God and I live my life on the assumption that he is there.
3. Weak Theist: I am very uncertain, but I am inclined to believe in God.
4. Pure Agnostic: God’s existence and non-existence are exactly equiprobable.
5. Weak Atheist: I do not know whether God exists but I’m inclined to be skeptical.
6. De-facto Atheist: I cannot know for certain but I think God is very improbable and I live my life under the assumption that he is not there.
7. Strong Atheist: I am 100% sure that there is no God.
Dawkins himself classifies people whose beliefs fall within the range of 1-2 as theists, those whose beliefs fall with the range of 3-5 are agnostics and those who are a 6 or 7 are atheists.
He says that he has never met a true '7'. He calls himself a '6.9'. He says that he is agnostic about God's existence on to the extent that he is agnostic about fairies at the bottom of his garden.