Period Calculator
Predict your next 6 periods based on your last period date and average cycle length. Plan ahead with ease.
How to Use the Period Calculator
Enter the first day of your last period, your average cycle length, and how many days your period typically lasts. The calculator will predict the start and end dates of your next six menstrual periods, helping you plan around important events.
The Extended Calculator below shows a visual 6-month period calendar and handles irregular cycles. The Professional Calculator adds cycle statistics (average, min, max, standard deviation), a symptom tracker, and warning flags for when to see a doctor.
6-Month Period Schedule
| # | Period Starts | Period Ends |
|---|---|---|
| Last | 28 Oct 2025 | 02 Nov 2025 |
| #1 | 25 Nov 2025 | 30 Nov 2025 |
| #2 | 23 Dec 2025 | 28 Dec 2025 |
| #3 | 20 Jan 2026 | 25 Jan 2026 |
| #4 | 17 Feb 2026 | 22 Feb 2026 |
| #5 | 17 Mar 2026 | 22 Mar 2026 |
How Future Periods Are Calculated
Next Period Start: Last Period Date + Cycle Length
Period End: Start Date + Period Duration − 1
Each subsequent period is calculated by adding the cycle length to the previous start date.
Example
Last period: 1 March | Cycle: 28 days | Duration: 5 days
Next period: 29 March – 2 April
Following period: 26 April – 30 April
Symptom Tracker Reference
Select symptoms you typically experience:
When to See a Doctor
Based on your data, consider seeing a doctor about:
- Heavy periods (menorrhagia) — may cause anaemia
Always consult a doctor if you experience:
- Bleeding between periods
- Periods lasting more than 7 days
- Soaking more than 1 pad/tampon per hour for several hours
- Severe pain that prevents normal activities
- No period for 3+ months (not pregnant)