Free Online Period Calculator — Track Your Menstrual Cycle Accurately
Period calculator helps you predict your next period dates, fertile window, ovulation day, and safe days based on your menstrual cycle length. Completely private, no signup needed, and designed for women across India and worldwide to take charge of their reproductive health.
Calculate Your Period Dates
Your Next Cycle Prediction
| Cycle | Period Start | Period End | Fertile Window | Ovulation | PMS Window | Next Period |
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How to Use the Period Calculator
Select Last Period Start Date
Click the date picker and select the first day of your most recent menstrual period. This is the day your bleeding started.
Enter Your Average Cycle Length
Enter the number of days in your typical menstrual cycle. The average is 28 days, but cycles can range from 21 to 45 days.
Enter Period Duration
Enter how many days your period bleeding usually lasts. The average is 5 days, with a typical range of 2 to 10 days.
Select Number of Cycles to Predict
Choose how many future cycles you want the calculator to predict, from 1 to 12 months ahead.
Click Calculate Period
Click the Calculate Period button to instantly see your predicted next period dates, fertile windows, ovulation days, and safe days.
Copy or Print Your Results
Use the Copy Results button to save your predictions or print the page for your personal health records.
Key Features of Our Period Calculator
100% Free Forever
Calculate unlimited period predictions without any charges, premium upgrades, or hidden subscription fees.
Accurate Predictions
Uses the medically recognized calendar method to predict periods, fertile windows, and ovulation with high accuracy.
Instant Results
Get your complete cycle predictions in under a second with no loading delays or waiting time required.
Complete Privacy
All calculations happen in your browser. No health data is ever sent to servers or stored anywhere online.
No Signup Needed
Start calculating immediately without creating accounts, verifying emails, or sharing any personal information.
Mobile Friendly
Fully responsive design works perfectly on smartphones, tablets, and desktops for tracking anywhere anytime.
How the Period Calculator Works
Next Period = Last Period Start + Cycle Length | Ovulation = Next Period − 14 days | Fertile Window = Ovulation − 5 days to Ovulation + 1 dayCalculation Components
- Next Period Date: Calculated by adding your average cycle length (in days) to the start date of your last period. This gives the expected first day of your next menstruation.
- Ovulation Day: Estimated as 14 days before the next expected period start date. This is based on the luteal phase, which is relatively constant at about 14 days for most women.
- Fertile Window: Spans from 5 days before ovulation to 1 day after ovulation (approximately 6 days total). Sperm can survive up to 5 days, and the egg lives for about 24 hours.
- PMS Window: Estimated as the 7 to 10 days before the next expected period. Premenstrual symptoms typically appear during this timeframe.
- Safe Days: Days that fall outside both the period days and the fertile window, where pregnancy probability is lowest. These are the remaining days in the cycle.
For example, if Priya from Pune has her last period starting on January 1st with a 30-day cycle, her next period would be predicted for January 31st. Her ovulation day would be approximately January 17th, and her fertile window would span from January 12th to January 18th. The PMS window would be from approximately January 21st to January 30th. This calculation repeats for each subsequent cycle.
Practical Examples
Regular 28-Day Cycle — Ananya, Delhi
Input: Last period: March 5, Cycle: 28 days, Duration: 5 days
Result: Next period: April 2 | Ovulation: March 19 | Fertile: March 14–20
Use Case: Ananya uses this to plan her travel schedule around her period dates and track her fertility awareness for family planning.
Longer 35-Day Cycle — Meera, Bengaluru
Input: Last period: Feb 10, Cycle: 35 days, Duration: 6 days
Result: Next period: March 17 | Ovulation: March 3 | Fertile: Feb 26–March 4
Use Case: Meera has a longer cycle and uses predictions to understand her unique pattern and prepare for PMS symptoms in advance.
Short 24-Day Cycle — Kavitha, Chennai
Input: Last period: April 1, Cycle: 24 days, Duration: 4 days
Result: Next period: April 25 | Ovulation: April 11 | Fertile: April 6–12
Use Case: Kavitha tracks her shorter cycles to anticipate period dates for important work presentations and social commitments.
International User — Sarah, London
Input: Last period: May 15, Cycle: 30 days, Duration: 5 days
Result: Next period: June 14 | Ovulation: May 31 | Fertile: May 26–June 1
Use Case: Sarah uses the calculator to plan her vacation and outdoor activities around her predicted menstrual dates for convenience.
What is a Period Calculator?
A period calculator is a health tool designed to help women and menstruating individuals predict their upcoming menstrual cycle dates, including the expected period start and end dates, the fertile window when pregnancy is most likely, the approximate ovulation day, PMS onset, and safe days. It uses the well-established calendar method, which is based on tracking cycle length patterns to estimate future dates with reasonable accuracy.
This free period calculator from StoreDropship is designed with the privacy and needs of Indian women in mind, while also serving users worldwide. Whether you are a college student in Mumbai trying to plan exams around your cycle, a working professional in Hyderabad managing your schedule, or someone trying to conceive, this tool provides valuable insights into your reproductive health without compromising your personal data.
The calculator is built to be simple and accessible for all users, regardless of technical knowledge. Simply enter your last period start date and average cycle length, and the tool instantly generates detailed predictions for up to 12 future cycles. All calculations are performed entirely within your web browser, ensuring that your sensitive health information never leaves your device. Medical professionals and health educators widely recommend cycle tracking as an important aspect of reproductive health awareness, and this tool makes it easy and free for everyone.