This menstrual cycle reference table shows the next period expected for a range of average cycle length values, assuming a first day of last period of 2025-01-01. Every figure is computed with the same engine that powers our Menstrual Cycle Calculator, so the numbers are exact.
| Average cycle length | Next period expected | Following period |
|---|---|---|
| 20 days | 21 Jan 2025 | 10 Feb 2025 |
| 21 days | 22 Jan 2025 | 12 Feb 2025 |
| 28 days | 29 Jan 2025 | 26 Feb 2025 |
| 42 days | 12 Feb 2025 | 26 Mar 2025 |
| 45 days | 15 Feb 2025 | 01 Apr 2025 |
How to use this table
Find the row closest to your average cycle length and read across to the next period expected. For a value between two rows, the real figure sits between them — or enter your exact numbers in the Menstrual Cycle Calculator for a precise answer.
Need a value that is not in the table? — the Menstrual Cycle Calculator does it instantly, for free, with the formula and a worked example built in.
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