The best days to conceive

Your best chance of conceiving is during the fertile window: roughly the five days before ovulation plus ovulation day itself. Sperm can live up to five days; the egg lives about a day — so intercourse before ovulation matters more than after.

Finding your fertile window

Ovulation typically happens in the second half of your cycle — MoodSwings estimates it by counting back from your next predicted period, because the luteal phase (ovulation → period) is more consistent than the first half of the cycle. That's why two people with the same cycle length can ovulate on the same day, while the "day 14" rule fails anyone whose cycle isn't exactly 28 days.

The fastest way to see your dates: the free ovulation calculator — enter your last period and cycle length and it maps your estimated window using the same counting method as the app.

What the estimate can and can't tell you

• It's a calendar estimate. Stress, travel, illness and irregular cycles all shift ovulation. A calculator can't see this month — it projects from your pattern.
• Signals beat math. Cervical mucus changes and ovulation tests (LH strips) confirm what a calendar only predicts. Many people combine both.
• Short cycles are different. In cycles under ~20 days a meaningful ovulation estimate isn't possible from dates alone — MoodSwings deliberately doesn't guess in that range, and neither should you.
• Irregular cycles need pattern-tracking. One-off calculators assume your next cycle matches your average. An app that learns your real pattern — including irregular ones — gives estimates that improve every month.

Making the window work for you

Aim for intercourse every 1–2 days across the fertile window rather than saving everything for ovulation day — the days before ovulation carry the highest probability. And be kind to yourselves: even perfectly-timed cycles have roughly a 20–30% chance per month for healthy couples under 35. Most conceive within a year.

If you've been trying for 12+ months (or 6+ months over 35), talk to a doctor — that's standard guidance, not a cause for alarm.