Ovulation tests (aka ovulation predictor kits) are available from pharmacies and some supermarkets, without a prescription. They use urine or saliva to test the level of luteinising hormone (LH) and/or oestrogen which increases 1-2 days before ovulation.
There are various ways you can predict ovulation without using tests, such as using the calendar method or apps. However, some women find these ways difficult and may feel more certain using ovulation tests.
Urine Ovulation Tests

Urine tests are more accurate than saliva tests. These are used like home pregnancy tests: you either pee on a stick or dip the stick into a cup of urine and the result will say whether you’re ovulating or approaching ovulation. Each brand has slightly different instructions. Always carefully read the instructions included with the product carefully before use.
Urine ovulation tests can become expensive, especially if your cycles are irregular. One test box may last 1 month at first which you could stretch to 2 months once you get better at predicting when you ovulate. Because my periods are regular and I’d been tracking my cycles for about 6 months already using apps, I usually tested 3-4 days before getting a positive ovulation test result.

Saliva ovulation tests detect changes in the salt concentration of saliva that occurs when the oestrogen level increases just before ovulation. Saliva is placed on a small slide that can be viewed through a magnifying lens (all part of the ovulation test). Dried saliva will crystallise into a fern-like pattern if there is a higher salt concentration (i.e. when there is a spike in oestrogen). Slight ferning indicates you’re approaching ovulation and strong ferning indicates you’re most fertile.
Some women find these tests difficult to use, or find the ferning patterns difficult to interpret. Always carefully read the instructions included with the product carefully before use.
Saliva ovulation tests are more expensive than urine ovulation tests but they’re reusable so are better value if you need to use them for several months.