Nepali Period Calculator (BS Date): Next Period, Ovulation & Fertile Window
Enter the first day of your last period as a Bikram Sambat (BS) date, and your usual cycle length. You get your next period, ovulation and fertile window in BS and in English dates. It runs in your browser, so nothing is sent or stored.
First day of your last period (BS)
Calculated in your browser. Nothing you enter is sent or stored. Estimates only, and not a method of contraception.
How the Nepali period calculator works
Most people in Nepal remember dates in Bikram Sambat, but a period cycle is counted in days. So the calculator converts the BS date you enter into an English (AD) date, adds your cycle length to find the next period, subtracts 14 days for ovulation, then converts each result back to BS. You see both calendars side by side.
The conversion matters because BS months are not a fixed length. Each BS month has 29, 30, 31 or 32 days, and the length of a given month changes from year to year. There is no formula for this. The official calendar is published as a table, and the calculator contains that table for 2070 to 2090 BS. As a check, 1 Baisakh 2083 BS falls on 14 April 2026.
The formula
- Next period = first day of last period + cycle length (in days)
- Ovulation = next period minus 14 days
- Fertile window = 5 days before ovulation up to 1 day after
For example, with a 28-day cycle starting on 1 Baisakh 2083 (14 April 2026), the next period is on 12 May 2026 and ovulation is around 28 April 2026. If the BS month were counted instead of days, the answer would depend on whether Baisakh has 30, 31 or 32 days that year. That is the mistake our article on tracking your period with the Nepali calendar explains.
If your cycles are irregular
The result is one date, but real cycles vary. If your cycle is sometimes 26 days and sometimes 34, try both numbers and treat the two answers as the range. The next period calculator has a box for this that shows the range directly, using English dates. Irregular periods are common and often harmless, but they are worth discussing with a doctor if they stay outside 21 to 35 days. See irregular cycles: when to see a doctor.
This is not contraception
The fertile window is an estimate from an average cycle. Ovulation can move, sperm can live up to five days, and the calculator cannot see your body. Do not use it to avoid pregnancy. Ask a doctor or local health worker about proven methods. See the fertile window and why it is not contraception.
When to see a doctor
See a doctor or health worker if your periods are regularly more than 35 days or less than 21 days apart, if you miss three periods in a row and are not pregnant, if bleeding lasts more than 7 days or is very heavy, or if pain stops you from doing normal things. For the sources we rely on, see our editorial policy.
Questions about the Nepali calculator
Can I enter my last period in Nepali (BS) date?
Yes. Choose the BS year, month and day of the first day of your last period. The calculator converts it to an English date, works out your next period, ovulation and fertile window, and shows every result in both BS and English dates.
Which BS years does the converter support?
It uses a month-length table for 2070 to 2090 BS (April 2013 to April 2034 in English dates). Dates outside that range are not converted.
Why not just add one month in BS?
BS months have 29 to 32 days and the length changes from year to year, so the same date next month is not a fixed number of days later. Counting your cycle in days and then converting the result is the reliable way.
How are ovulation and the fertile window worked out?
Ovulation is estimated at 14 days before the next period. The fertile window is from 5 days before ovulation to 1 day after. These are estimates for awareness and not contraception.
Is my date stored or sent anywhere?
No. The calculation and the BS conversion run in your browser. Nothing is sent or stored, and this site has no analytics.
Track in BS dates without calculating. Cycella is a free Android period tracker for Nepal with no account and no ads. In Nepali, the Today screen shows the BS date next to the English date, and it works offline. It is free on Google Play. See Cycella in Nepal.