Predict your ovulation day and fertile window for six cycles.
Ovulation usually happens 14 days before your next period. With a 28-day cycle that began on 1 January, ovulation is on Thursday, 15 January 2026 and your fertile window runs from 10 to 16 January.
The Ovulation Calculator predicts your most fertile days. Enter the first day of your last period, your average cycle length and your luteal phase, and it lists the next six cycles with the period start date, fertile window, ovulation day and the date the next period is due.
Ovulation can move because of stress, illness, travel or irregular cycles, so confirm with ovulation test kits or temperature tracking if you are trying to conceive. This tool is not a contraceptive method. See the Conception Calculator, the Period Calculator and the Due Date Calculator.
The calculator applies the standard published formulas step by step.
| Item | Value |
|---|---|
| Cycle length | 28 days |
| Luteal phase | 14 days |
| Ovulation day in a cycle | Day 14 of the cycle |
| Fertile window | 5 days before ovulation to 1 day after |
| Cycle | Period starts | Fertile window | Ovulation | Next period |
|---|---|---|---|---|
| 1 | Thursday, 1 January 2026 | Saturday, 10 January 2026 – Friday, 16 January 2026 | Thursday, 15 January 2026 | Thursday, 29 January 2026 |
| 2 | Thursday, 29 January 2026 | Saturday, 7 February 2026 – Friday, 13 February 2026 | Thursday, 12 February 2026 | Thursday, 26 February 2026 |
| 3 | Thursday, 26 February 2026 | Saturday, 7 March 2026 – Friday, 13 March 2026 | Thursday, 12 March 2026 | Thursday, 26 March 2026 |
| 4 | Thursday, 26 March 2026 | Saturday, 4 April 2026 – Friday, 10 April 2026 | Thursday, 9 April 2026 | Thursday, 23 April 2026 |
| 5 | Thursday, 23 April 2026 | Saturday, 2 May 2026 – Friday, 8 May 2026 | Thursday, 7 May 2026 | Thursday, 21 May 2026 |
| 6 | Thursday, 21 May 2026 | Saturday, 30 May 2026 – Friday, 5 June 2026 | Thursday, 4 June 2026 | Thursday, 18 June 2026 |
| Cycle | Ovulation |
|---|---|
| 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 |
Around day 14, counting the first day of your period as day 1.
Around day 21, because ovulation is about 14 days before the next period, not always on day 14.
About six days: the five days before ovulation and the day of ovulation.
The time between ovulation and your next period, usually 12–14 days and fairly constant for each person.
Ovulation predictor kits detect the LH surge; a sustained rise in morning body temperature and clear, stretchy mucus are other signs.
No. Predictions can be wrong and sperm survive for days. Use reliable contraception if you want to avoid pregnancy.
It uses the published formula: ovulation day = cycle length − luteal phase fertile window = ovulation − 5 to ovulation + 1 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.
