When to start 20 day tests?

Thanks for contacting us about our 20 count package of Clearblue Digital Ovulation Tests, Christa.  We've recently changed the instruction leaflet to use your cycle length to determine which day to begin testing.  In order to let you know when to begin testing, what is your usual cycle length?  To calculate your cycle length, consider the first day of your period as day 1 then count through to the day before your next period starts.  The total number of days is your cycle length.