How to Convert BS to AD Dates (and Back) Easily
If you were born in Nepal, your citizenship, school records, and birth certificate almost certainly use a Bikram Sambat (BS) date. The moment you apply for a visa, a foreign job, or a university abroad, you need that same date in the Gregorian (AD) calendar. Getting it right matters.
The good news: the two calendars track the same days, just counted differently. The catch is that there is no single tidy formula that works for every date. This guide explains the roughly 56.7-year gap, why a fixed offset breaks down, and how to convert accurately in both directions.
What Is the Difference Between BS and AD?
Bikram Sambat runs about 56 years and 8.5 months ahead of the Gregorian AD calendar. So the year 2026 AD overlaps with 2082-2083 BS. BS is a lunisolar Hindu calendar with months of variable length, while AD is a purely solar calendar with fixed month lengths. That single difference is why conversion is tricky.
The BS calendar uses 12 months, from Baisakh through Chaitra, and its new year begins in mid-April rather than on 1 January. If you want the full month-by-month picture first, read our breakdown of the 12 Nepali calendar months in order, and for the calendar's history see what the Bikram Sambat calendar is.
Why Is the Offset Roughly 56.7 Years?
The offset exists because Bikram Sambat begins counting from 57 BC, the legendary start of King Vikramaditya's era, while AD counts from year 1. That head start of about 57 years carries forward today. Because the BS new year falls in mid-April, not January, the exact gap shifts within a single AD year.
Here is the part most people miss. From January to mid-April, the gap is about 56 years and 8 months because the BS year has not yet rolled over. After Baisakh 1 (mid-April), the BS year increments, so for the rest of the AD year the gap is about 57 years. This is why people say about 56.7 years as an average, not an exact constant.
| Period in 2026 AD | Corresponding BS year | Approx. gap |
|---|---|---|
| 1 Jan to mid-April 2026 | 2082 BS | ~56 years 8 months |
| Mid-April to 31 Dec 2026 | 2083 BS | ~57 years |
Why Doesn't a Fixed Formula Work?
A fixed add-or-subtract formula fails because BS month lengths are not constant. Unlike AD, where April always has 30 days and July always has 31, a Bikram Sambat month can have 29, 30, 31, or 32 days, and that count changes from year to year. So you cannot simply add a set number of days to land on the right AD date.
Variable month lengths
The length of each BS month is determined by the sun's movement through the zodiac (sankranti), not by a repeating pattern. Baisakh might have 31 days one year and 30 or 32 in another. Because of this, conversion tables are computed and published year by year, and software relies on stored data rather than arithmetic alone.
The approximate formula and its limits
For a quick mental estimate you can subtract about 56 years 8 months from a BS date to get the AD date, or add the same to go the other way. This gets you the right ballpark, often within a day or two. For anything official, a passport, a contract, an exam form, that margin of error is unacceptable. You need an exact lookup.
How Do You Convert BS to AD with a Worked Example?
The reliable method is to use a verified conversion table or app rather than raw arithmetic. To see why, take a real example. Suppose a birth date reads 2050 Baisakh 1 BS. The rough estimate (subtract 56 years 8 months) suggests early 1994. The exact answer is 13 April 1993 AD, which a quick subtraction would have missed.
Worked example: BS to AD
Take the BS date you want, for example 2080 Mangsir 15.
A rough estimate lands you around late November to early December 2023.
The exact converted date is 1 December 2023 AD. The difference between the estimate and the truth is exactly why you confirm with a table.
Worked example: AD to BS
Take an AD date, for example 15 August 2026.
Since this is after mid-April, add about 57 years to estimate 2083 BS.
The exact date is 30 Shrawan 2083 BS. The day-of-month never maps one-to-one, so always verify the day, not just the year.
What Is the Easiest Way to Convert Accurately?
The easiest accurate method is a digital converter that holds the official year-by-year month-length data, so you avoid the variable-length problem entirely. The Nepali Calendar (Katigate) app converts BS to AD and back instantly, with no manual arithmetic, and it stays correct across the month rollovers that trip up fixed formulas.
Beyond conversion, the app shows daily Panchang, Rashifal, festival dates, and auspicious Saait, all anchored to the correct BS-to-AD mapping. You can explore the calendar and converter from the Nepali Calendar home page, and learn the full feature set in our guide to using the Nepali Calendar app.
One more thing worth knowing: Bikram Sambat is not the only era used in Nepal. If you have seen dates that do not match either BS or AD, they may be in Nepal Sambat. Our comparison of Bikram Sambat vs Nepal Sambat vs AD clears up which calendar you are actually reading.
Explore more on Nepali Calendar (Katigate)
Frequently Asked Questions
How many years ahead is BS from AD?
Bikram Sambat is about 56 years and 8.5 months ahead of the Gregorian AD calendar, often rounded to roughly 56.7 years. Because the BS new year falls in mid-April rather than January, the exact gap is about 56 years 8 months early in the AD year and about 57 years after mid-April.
Can I convert BS to AD with a simple formula?
You can get a rough estimate by subtracting about 56 years 8 months, but it is not exact. Bikram Sambat months vary between 29 and 32 days from year to year, so no fixed formula maps every date correctly. For official documents, always confirm with a verified converter or table.
Why does my converted date differ by a day or two?
A day or two of drift almost always comes from using the average offset instead of the real month-length data for that specific year. Since BS month lengths change annually, only a converter that stores the official data per year returns the exact day. Manual subtraction will frequently be off.
What is the BS year for 2026 AD?
Most of 2026 AD falls in 2083 BS, but January to mid-April 2026 still belongs to 2082 BS. The change happens on Baisakh 1, the Nepali new year in mid-April. This rollover is exactly why you must check the day and month, not just add 57 to the year.