It has been quite accurate for me (I've used 1 per week). Apparently the brackets for hcg are 25-200= 1-2 weeks since conception/3-4 weeks preg; 200-2000 = 2-3 weeks since conception/4-5 weeks preg; 2000+ = 3+ weeks since conception/5+ weeks preg. I lined up the days I took them with the average days based on beta base that you would expect to get to the next bracket and it has worked for me.
I have used clearblue digital tests every time I have been pregnant (1 new pregnancy now, 1 missed miscarriage, 1 ectopic) - They were spot on for me every time.
I found out about my pregnancy when I was almost 12 weeks along and the clear blue I took said 3+ weeks when I took it. I knew based on the last time I had a period I was at least 6 weeks and at my dating scan a week later was 12 weeks 4 days. Technically it's correct, as its indicating 3 or more weeks pregnant - I'm pretty sure the instructions indicated that there were only a few options anyway it will only say "1-2", "2-3" or "3+".
Re: Has anyone use clearblue digital that tells you how many weeks you are? I'm unsure on my dates xx