How long do you ovulate?

Brittney

Okay so I am undergoing some fertility treatments. First day of last period was Jan 7, days 3-7 I took Femara, last Saturday I gave myself the ovidrel injection. I have been using opks to make sure I ovulate. I have some really good results but how long does ovulation last? I was thinking 12-48 hours but I keep getting strong positives on my opk.