A good rule is to wait until your period is a week late. Those tests aren't cheap and it is a waste of money to test and then have your period start the next day.
How long do you have to wait before you can tell if you are pregnant?
Yes Moga is right. Wait till you are a week late. If you do a home test and it comes up positive make an appointment and see you doctor for a blood test, if that comes up positive your 99.99% sure you are positive.
Wait to see if you have a period.