s only tell you there is a CHANCE that you are going to
ovulate...they can not determine that
you actual have or will. BBT charting can tell
you that
you DID in fact ovulate on a certain day. While it doesn't give you a heads up and let you know ahead of time, you will learn to see a pattern of when you ovulate. By using a combo of opk's and bbt you can predict when you might ovulate and then confirm that you in fact did. Good luck!