If you would like to use a Clearblue® Ovulation Test and are wondering when you should start testing, this tool can help you.
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 Ovulation Calculator tool*.
How to determine which day to start testing
Informations
E.g., 09/09/2026
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’re 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.
Identify your 2 most fertile days
Count the first day of your next period as Day 1
Typically identifies 4 or more fertile days3
Count the first day of your next period as Day 1
Identify your 2 most fertile days
Typically identifies 4 or more fertile days3
| Start of your last period | |
| What’s your usual cycle length? | 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.
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