A free, private period and ovulation tracker
Sakhi (सखी — a close female friend) is a simple period tracker and ovulation calculator that runs entirely in your browser. Enter your last period and your usual cycle length, and Sakhi estimates your next periods, your ovulation day and your fertile window, and lays them out on a clean, colour-coded calendar.
The most important thing first: your data never leaves your device. Your dates, logs and notes are saved only in this browser's local storage. There is no account, no server and no cloud — we genuinely cannot see your information.
How Sakhi calculates your cycle
- Next period — your last period start plus your average cycle length (default 28 days). Each future period is one more cycle length forward.
- Ovulation day — estimated as 14 days before your next period starts (the luteal phase is fairly consistent at about 14 days).
- Fertile window — the six days from 5 days before ovulation up to 1 day after, because sperm can survive a few days and the egg lives about a day.
- Your real average — once you log 2 or more period starts, Sakhi uses the average gap between your own cycles instead of the slider.
The phases of your cycle
- Menstrual — your period days, when pregnancy chance is low.
- Follicular — after your period, building up to ovulation.
- Fertile / Ovulation — your most fertile days, with the highest chance of pregnancy.
- Luteal — after ovulation, leading into your next period.
Frequently asked questions
Is Sakhi free and private?
Yes. Sakhi is completely free and works without an account. All the dates, logs and notes you enter are stored only in your browser on your device and are never uploaded to any server.
How is ovulation calculated?
Ovulation is estimated as 14 days before your next predicted period. This works because the time from ovulation to the next period (the luteal phase) is fairly stable, usually around 14 days, even when cycle lengths differ.
What is the fertile window?
The fertile window is the span of days when pregnancy is most likely — roughly the five days leading up to ovulation plus the day of and the day after. Sakhi shows it as a six-day teal band on the calendar.
What are "safe days"?
"Safe days" usually refers to the days outside the fertile window. Because cycles vary and ovulation can shift, Sakhi's estimates should not be used as a contraceptive method. Always speak to a doctor about reliable birth control.
Does it work for irregular periods?
Sakhi can still give estimates, but they are less accurate when cycles are irregular. Logging several real periods helps Sakhi learn your average, and a doctor can advise on irregular cycles.
Can I use it offline and install it?
Yes. You can add Sakhi to your home screen and open it like an app, and it keeps working offline because everything runs on your device.