islaLast period started in December: when is the next one?
Find the day your last period started in the left column and your usual cycle length along the top. The date where they meet is the estimated start of your next period. December has 31 days.
With a 21-day cycle, a period that starts on December 1 to 10 is followed by the next one before December ends. With a 28-day cycle, a period that starts on December 1 to 3 is followed by the next one before December ends.
| Last start | 21-day cycle | 25-day cycle | 28-day cycle | 30-day cycle | 32-day cycle | 35-day cycle |
|---|---|---|---|---|---|---|
| Dec 1 | Dec 22 | Dec 26 | Dec 29 | Dec 31 | Jan 2 | Jan 5 |
| Dec 2 | Dec 23 | Dec 27 | Dec 30 | Jan 1 | Jan 3 | Jan 6 |
| Dec 3 | Dec 24 | Dec 28 | Dec 31 | Jan 2 | Jan 4 | Jan 7 |
| Dec 4 | Dec 25 | Dec 29 | Jan 1 | Jan 3 | Jan 5 | Jan 8 |
| Dec 5 | Dec 26 | Dec 30 | Jan 2 | Jan 4 | Jan 6 | Jan 9 |
| Dec 6 | Dec 27 | Dec 31 | Jan 3 | Jan 5 | Jan 7 | Jan 10 |
| Dec 7 | Dec 28 | Jan 1 | Jan 4 | Jan 6 | Jan 8 | Jan 11 |
| Dec 8 | Dec 29 | Jan 2 | Jan 5 | Jan 7 | Jan 9 | Jan 12 |
| Dec 9 | Dec 30 | Jan 3 | Jan 6 | Jan 8 | Jan 10 | Jan 13 |
| Dec 10 | Dec 31 | Jan 4 | Jan 7 | Jan 9 | Jan 11 | Jan 14 |
| Dec 11 | Jan 1 | Jan 5 | Jan 8 | Jan 10 | Jan 12 | Jan 15 |
| Dec 12 | Jan 2 | Jan 6 | Jan 9 | Jan 11 | Jan 13 | Jan 16 |
| Dec 13 | Jan 3 | Jan 7 | Jan 10 | Jan 12 | Jan 14 | Jan 17 |
| Dec 14 | Jan 4 | Jan 8 | Jan 11 | Jan 13 | Jan 15 | Jan 18 |
| Dec 15 | Jan 5 | Jan 9 | Jan 12 | Jan 14 | Jan 16 | Jan 19 |
| Dec 16 | Jan 6 | Jan 10 | Jan 13 | Jan 15 | Jan 17 | Jan 20 |
| Dec 17 | Jan 7 | Jan 11 | Jan 14 | Jan 16 | Jan 18 | Jan 21 |
| Dec 18 | Jan 8 | Jan 12 | Jan 15 | Jan 17 | Jan 19 | Jan 22 |
| Dec 19 | Jan 9 | Jan 13 | Jan 16 | Jan 18 | Jan 20 | Jan 23 |
| Dec 20 | Jan 10 | Jan 14 | Jan 17 | Jan 19 | Jan 21 | Jan 24 |
| Dec 21 | Jan 11 | Jan 15 | Jan 18 | Jan 20 | Jan 22 | Jan 25 |
| Dec 22 | Jan 12 | Jan 16 | Jan 19 | Jan 21 | Jan 23 | Jan 26 |
| Dec 23 | Jan 13 | Jan 17 | Jan 20 | Jan 22 | Jan 24 | Jan 27 |
| Dec 24 | Jan 14 | Jan 18 | Jan 21 | Jan 23 | Jan 25 | Jan 28 |
| Dec 25 | Jan 15 | Jan 19 | Jan 22 | Jan 24 | Jan 26 | Jan 29 |
| Dec 26 | Jan 16 | Jan 20 | Jan 23 | Jan 25 | Jan 27 | Jan 30 |
| Dec 27 | Jan 17 | Jan 21 | Jan 24 | Jan 26 | Jan 28 | Jan 31 |
| Dec 28 | Jan 18 | Jan 22 | Jan 25 | Jan 27 | Jan 29 | Feb 1 |
| Dec 29 | Jan 19 | Jan 23 | Jan 26 | Jan 28 | Jan 30 | Feb 2 |
| Dec 30 | Jan 20 | Jan 24 | Jan 27 | Jan 29 | Jan 31 | Feb 3 |
| Dec 31 | Jan 21 | Jan 25 | Jan 28 | Jan 30 | Feb 1 | Feb 4 |
Periods often start a few days either side of an estimate. Every date here is an estimate from a typical cycle length. It is not birth control and it is not medical advice.
Log the first day of each period in Isla and it keeps the next estimate, a range and the calendar up to date on your iPhone. No account and no ads.
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