Which day of my cycle should I start testing ovulation with kits?

Trying to get pregnant or just tracking your ovulation? Timing is everything — and knowing exactly when to test for ovulation based on your unique cycle length can make all the difference.

Let’s break it down.

What Is the Best Day to Test Ovulation?

Ovulation usually happens 14 days before your next period starts. But since every woman’s cycle length is different, your ovulation day (and the day you should start testing) depends on how long your cycle is.

For example:

• If you have a 28-day cycle, ovulation is likely around day 14.

• If your cycle is 32 days, ovulation may happen closer to day 18.

But here’s the catch: ovulation can shift. Stress, travel, illness, and even sleep can affect it. That’s why using ovulation test kits (LH kits) is one of the most reliable ways to catch your fertile window.

When Should You Start Testing for Ovulation?

Use the table below to know exactly which day of your cycle to start testing:

Cycle Length	Approx Ovulation Day	Start Testing From
24 days	Day 10	Day 8
25 days	Day 11	Day 9
26 days	Day 12	Day 10
27 days	Day 13	Day 11
28 days	Day 14	Day 12
29 days	Day 15	Day 13
30 days	Day 16	Day 14
31 days	Day 17	Day 15
32 days	Day 18	Day 16
33 days	Day 19	Day 17
34 days	Day 20	Day 18
35 days	Day 21	Day 19

Start testing 3–5 days before your expected ovulation, and keep testing daily (once or twice a day) until you get a positive result.

How Do Ovulation Test Kits Work?

Ovulation kits detect a hormone called LH (luteinizing hormone), which surges 24–36 hours before ovulation. A positive test tells you you're entering your most fertile window — aka your best chance to conceive.

Pro tip: Test between 10 AM and 8 PM, and try to test around the same time every day.

Why You Shouldn’t Rely on Apps Alone

While period-tracking apps are useful, they predict ovulation based on averages. Your body is not average — it’s unique. That’s why actual hormone testing is more accurate, especially if you're actively trying to conceive.

Final Tips

• Track your periods for at least 2–3 months to understand your average cycle length.

• Use ovulation kits like WHEN am I ovulating? for real-time confirmation.

• Have sex during your fertile window (a few days before and on ovulation day).

To find out which day of your cycle to test ovulation, subtract 14 from your total cycle length. Start testing 3–5 days before that.

Ovulation can vary, but testing with an LH kit is the most accurate way to identify your fertile window.