How to work out which day to start testing
If you would like to use a Clearblue Ovulation Test and are wondering when you should start testing, this tool can help you.
Just answer the two questions below and let us tell you when you should start testing.
How to determine which day to start testing
Informations
E.g., 2026-11-11
If you don't know your cycle length, we suggest you wait for your next cycle and note the day your period starts (Day 1) and the length of this cycle before using this online tool*.
To measure the length of your menstrual cycle, count from the day your period starts to the day before your next period starts.
If you don't know your menstrual cycle length, wait until you've had at least one cycle, then come back to use this calculator. If your cycle length varies by more than three days, choose the shortest cycle you've had in the last six months to work out when to start testing.
In this cycle, you’ve missed the ideal date to start testing.
We advise you to wait for your next cycle before using Clearblue Ovulation Tests, as it is possible that you missed your LH surge in this cycle.
Pinpoints your 2 most fertile days
Count the first day of your next period as Day 1
Typically identifies 4 or more fertile days2
Count the first day of your next period as Day 1
Pinpoints your 2 most fertile days
Typically identifies 4 or more fertile days2
| Start of your last period | |
| Usually, how long is your cycle? | days |
Results are based on the information you have provided.
*This tool is for guidance purposes. Always use the leaflet provided with your product to work out when you can test.
Advanced Digital Ovulation Test
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Having sex at the right time of your cycle is key, so identifying your fertile days with an ovulation test will help you get pregnant faster.
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- * If you wish to start using Clearblue Ovulation Tests before you know your cycle length, we recommend that you start testing on Day 10. However, without determining your cycle length, it is possible that you may miss your LH surge because you have started testing too late, or you may need to start a new pack to continue testing.