Nope, it's not possible to guess solely on the line of an opk. For some women, they notice the line gradualllly get darker up to O date, but this happens month to month. But if you haven't noticed it before I'd say no, because LH is always present in the body and it fluctuates regularly, when the egg is about to come that's when it shoots up sometimes it stays up for a while sometimes not. Last cycle I had high LH through my midcycle, and this time I have only had one day almost + and the rest of the lines are barely visible. So it varies so much, you'd just have to watch yyyour own body signs. Sorry for the late response!