Ovulation in a 30-day cycle: day 16
A 30-day cycle means ovulation around day 16. Following the classic day-14 advice would put your best days two days too early.
Start ovulation tests on about day 13; a pregnancy test is reliable from day 31.
Ovulation is usually about 14 days before the next period, so in a 30-day cycle it falls on day 16 — 2 days later than in a 28-day cycle. A 30-day cycle is within the usual adult range of about 21–35 days.
Your 30-day cycle, phase by phase
| Phase | Cycle days |
|---|---|
| Period (typical) | Days 1–5 |
| Follicular phase | Days 1–15 (15 days) |
| Fertile window | Days 11–17, best on days 14–16 |
| Ovulation | Day 16 |
| Luteal phase | Days 17–30 (14 days) |
Start LH ovulation tests around day 13; a positive result on day 14 or 15 points to ovulation on day 16.
If your cycle is sometimes 28 or 32 days
Few cycles are identical every month. If yours ranges between 28 and 32 days, ovulation could fall anywhere from day 14 to day 18, which widens your possible fertile days to days 9 to 19. Base the start of ovulation testing on your shortest recent cycle (day 11), and expect your period between day 29 and day 33.
| Cycle length | Ovulation | Fertile window |
|---|---|---|
| 28 days | Day 14 | Days 9–15 |
| 29 days | Day 15 | Days 10–16 |
| 30 days | Day 16 | Days 11–17 |
| 31 days | Day 17 | Days 12–18 |
| 32 days | Day 18 | Days 13–19 |
Example: a 30-day cycle starting today
| Period starts (day 1) | |
|---|---|
| Start ovulation tests (day 13) | |
| Fertile window (days 11–17) | – |
| Estimated ovulation (day 16) | |
| Next period / test day (day 31) |
Test for pregnancy from day 31 — see the Pregnancy Test Calculator for exact dates.