Estimate when you are most likely to conceive and your possible due date.
Ovulation usually happens about 14 days before the next period. With a 28-day cycle starting 1 January, the most likely conception day is Thursday, 15 January 2026, with a fertile window of 10–16 January.
Conception is most likely during your fertile window — the five days before ovulation and the day of ovulation itself. Enter the first day of your last period, your usual cycle length and your luteal phase and this calculator shows the ovulation day, fertile window, the days implantation would occur, when to test and the due date if you conceive this cycle.
Ovulation shifts from cycle to cycle, so use this as a guide and consider ovulation tests or tracking mucus changes. See your full predicted calendar with the Ovulation Calculator, predict periods with the Period Calculator and work backwards from a due date with the Pregnancy Conception Calculator.
The calculator applies the standard published formulas step by step.
| Item | Value |
|---|---|
| Cycle length | 28 days |
| Ovulation (cycle length − luteal phase) | Thursday, 15 January 2026 |
| Fertile window (5 days before to 1 day after ovulation) | Saturday, 10 January 2026 – Friday, 16 January 2026 |
| Implantation, if conception happens | Wednesday, 21 January 2026 – Tuesday, 27 January 2026 |
| Next period due (if not pregnant) | Thursday, 29 January 2026 |
| Earliest reliable pregnancy test | Thursday, 29 January 2026 |
| Due date if you conceive this cycle | Thursday, 8 October 2026 |
| Cycle | Ovulation day |
|---|---|
| 26-day cycle | Tuesday, 13 January 2026 |
| 28-day cycle | Thursday, 15 January 2026 |
| 30-day cycle | Saturday, 17 January 2026 |
| 32-day cycle | Monday, 19 January 2026 |
| 35-day cycle | Thursday, 22 January 2026 |
In the five days before ovulation and on the day of ovulation. The two days just before ovulation have the highest chance.
Counting back 14 days from your next period gives an estimate. Ovulation test strips, basal body temperature and cervical mucus give more precision.
About 12–24 hours after ovulation, while sperm can survive up to 5 days.
About 6–12 days after ovulation, when the fertilised egg attaches to the womb lining.
From the day your period is due, or about 14 days after ovulation, for the most reliable result.
If you are under 35 and have not conceived after 12 months of trying, or over 35 after 6 months, or you have irregular periods or other concerns.
It uses the published formula: ovulation = LMP + (cycle length − luteal phase) The full method and a worked example are shown on this page.
No. The calculator gives general estimates for information and education. It cannot diagnose or treat anything, so please speak to a doctor or qualified professional about your own health.
Yes. Choose centimetres or feet and inches for height, and kilograms, pounds or stone for weight; the results are converted for you.
No. Everything is calculated in your browser and nothing you enter is uploaded or saved.
