How to Track Ovulation: OPKs, BBT, Cervical Mucus, and Apps
The proven ways to find your fertile window — OPKs, cervical mucus, BBT, and apps — and what each one actually tells you.
There are a few proven ways to find your fertile window, and a lot of noise to cut through. This page covers the tools that work, what each one tells you, and how to use them without overcomplicating it.
How do LH strips (ovulation tests) work?
OPKs (ovulation predictor kits) detect the LH surge that occurs 24–36 hours before ovulation. A positive test means: have sex today and tomorrow. Most people start testing too late in their cycle — start a few days before you expect to ovulate, not on the day. If your OPK seems positive continuously, PCOS may be the reason: elevated baseline LH can produce what look like persistent positive results.
What is the fertile window and how long does it last?
The fertile window is approximately 6 days — the 5 days before ovulation and the day of ovulation itself. The highest-probability days are the 2–3 days immediately before ovulation. The goal of tracking is simply to identify when you're in that window. You don't need to track obsessively — OPKs plus paying attention to your body is the sweet spot.
How do you track ovulation without an app?
Cervical mucus is your body's real-time fertility signal and costs nothing. Clear, stretchy, slippery mucus — often compared to raw egg white — indicates the fertile window is open. This changes across the cycle and becomes easy to notice once you're looking. Combined with OPKs, it gives you two independent signals pointing to the same window.
What does cervical mucus tell you about ovulation?
Cervical mucus changes in response to estrogen: it's dry or sticky early in the cycle, becomes progressively more fluid as ovulation approaches, and peaks at clear, stretchy, and slippery at peak fertility. After ovulation, it becomes thick and opaque again under the influence of progesterone. The fertile-quality mucus is what allows sperm to survive and travel — without it, sperm can't reach an egg.
How accurate are BBT charts for timing intercourse?
Basal body temperature (BBT) tells you ovulation already happened — not that it's coming. The temperature rise occurs after ovulation, which means it's retrospective. BBT is genuinely useful for identifying your ovulation pattern over multiple cycles and confirming that ovulation is occurring, but it doesn't help you time this cycle's fertile window in real time. Use it alongside OPKs, not instead of them.
How often should you have sex when trying to conceive?
Every 1–2 days during the fertile window is the most effective approach. Daily and every-other-day intercourse produce comparable results — so the pressure to perform on a specific day isn't warranted. Sharing what you're seeing — "I got a positive OPK today" — keeps a partner in the loop without making sex feel clinical.
What is the best time to have sex to get pregnant?
The 2–3 days before ovulation are the highest-probability days. Sperm survive 3–5 days in fertile cervical mucus, so being early is better than being late. Sex on the day of ovulation alone misses most of the window. If you're using OPKs, a positive test means the next 24–36 hours matter.