Forecast your next 12 period start dates from the first day of your last period and your average cycle length — with the ovulation day and fertile window marked for each month.
Enter your data
Enter the first day of your last period and your average cycle length (usually 28 days) to forecast the next 12 periods.
The forecast assumes each cycle equals your average length and estimates ovulation about 14 days before the next period. It is an estimate, not a contraceptive method — real cycles vary from month to month.
Next period: 29 January 2026Predicted period start, ovulation day and fertile window for each of the next 12 cycles.
| Period start | Ovulation | Fertile window |
|---|---|---|
| 1 January 2026 | 15 Jan | 10 Jan – 16 Jan |
| 29 January 2026 | 12 Feb | 7 Feb – 13 Feb |
| 26 February 2026 | 12 Mar | 7 Mar – 13 Mar |
| 26 March 2026 | 9 Apr | 4 Apr – 10 Apr |
| 23 April 2026 | 7 May | 2 May – 8 May |
| 21 May 2026 | 4 Jun | 30 May – 5 Jun |
| 18 June 2026 | 2 Jul | 27 Jun – 3 Jul |
| 16 July 2026 | 30 Jul | 25 Jul – 31 Jul |
| 13 August 2026 | 27 Aug | 22 Aug – 28 Aug |
| 10 September 2026 | 24 Sept | 19 Sept – 25 Sept |
| 8 October 2026 | 22 Oct | 17 Oct – 23 Oct |
| 5 November 2026 | 19 Nov | 14 Nov – 20 Nov |
Indicative estimate, not medical advice. Period dates are forecast from your average cycle length; real cycles vary from month to month. It is not a contraceptive method — do not rely on it to avoid pregnancy. Instant in-browser calculation, no account.
✚ Results are for informational purposes and do not replace medical advice. For health decisions, consult a doctor.
Each period is projected by adding your cycle length to the previous start date, with ovulation set about 14 days before the following period:
For a 28-day cycle, each period starts 28 days after the last, ovulation falls around day 14, and the fertile window runs roughly from day 9 to day 15.
It adds your average cycle length to the first day of your last period to project the next start date, then repeats that step to build a forecast for the coming months.
It lists your next 12 period start dates, so roughly a year ahead. For each one it also shows the estimated ovulation day and the fertile window around it.
Ovulation is placed about 14 days before the next period. For a 28-day cycle that is around day 14, and the fertile window covers the 5 days before ovulation plus ovulation day.
Use your average length, counted from the first day of one period to the first day of the next. Values from 20 to 45 days are accepted; 28 days is the default and a common average.
It is indicative. The method assumes every cycle equals your average length, so real dates drift when cycles are longer, shorter or irregular. The further ahead a date is, the more it can shift.
No. The fertile window is an estimate for planning or awareness, not a birth-control method. Sperm survival and cycle variation make it unreliable for avoiding pregnancy — use a proven method and consult your doctor.