Ovulation in a 38-day cycle: day 24
A 38-day cycle suggests ovulation around day 24 — and fewer ovulations a year than shorter cycles, which can mean conceiving takes longer.
If you are trying for a baby and your cycles are usually this long, a doctor or nurse can check whether you are ovulating.
Ovulation is usually about 14 days before the next period, so in a 38-day cycle it falls on day 24 — 10 days later than in a 28-day cycle. A 38-day cycle is longer than the usual adult range of about 21–35 days. Longer cycles usually mean ovulation happens later — and sometimes less regularly — so it is worth talking to a doctor or nurse if your cycles are regularly this long, especially if you are trying to conceive.
Your 38-day cycle, phase by phase
| Phase | Cycle days |
|---|---|
| Period (typical) | Days 1–5 |
| Follicular phase | Days 1–23 (23 days) |
| Fertile window | Days 19–25, best on days 22–24 |
| Ovulation | Day 24 |
| Luteal phase | Days 25–38 (14 days) |
Start LH ovulation tests around day 21; a positive result on day 22 or 23 points to ovulation on day 24.
If your cycle is sometimes 36 or 40 days
Few cycles are identical every month. If yours ranges between 36 and 40 days, ovulation could fall anywhere from day 22 to day 26, which widens your possible fertile days to days 17 to 27. Base the start of ovulation testing on your shortest recent cycle (day 19), and expect your period between day 37 and day 41.
| Cycle length | Ovulation | Fertile window |
|---|---|---|
| 36 days | Day 22 | Days 17–23 |
| 37 days | Day 23 | Days 18–24 |
| 38 days | Day 24 | Days 19–25 |
| 39 days | Day 25 | Days 20–26 |
| 40 days | Day 26 | Days 21–27 |
Example: a 38-day cycle starting today
| Period starts (day 1) | |
|---|---|
| Start ovulation tests (day 21) | |
| Fertile window (days 19–25) | – |
| Estimated ovulation (day 24) | |
| Next period / test day (day 39) |
Test for pregnancy from day 39 — see the Pregnancy Test Calculator for exact dates.