BC to AD Calculator

Count the years between two dates on either side of the BC and AD boundary. The BC to AD calculator handles the missing year 0, which trips up most mental math.

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From

To

Years between
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How to use the BC to AD Calculator

  1. Enter the From year and pick BC or AD.
  2. Enter the To year and its era.
  3. Press Calculate. The number of years appears, with the astronomical year numbers used.

How it works

astronomical year = 1 − BC year   (1 BC = 0, 2 BC = −1)
astronomical year = AD year
years between = astronomical(to) − astronomical(from)

The calendar goes straight from 1 BC to AD 1. Astronomers renumber BC years so that 1 BC is year 0, which makes subtraction work.

Examples

  • 500 BC to AD 2026: 2026 − (−499) = 2,525 years, not 2,526.
  • 1 BC to AD 1: 1 year.
  • The founding of Rome in 753 BC to the fall of the Western Roman Empire in AD 476: 1,228 years.

BC, AD, BCE, and CE

BCE (Before Common Era) and CE (Common Era) use the same numbers as BC and AD. Only the labels differ, so 500 BCE is the same year as 500 BC.

Limitations

  • Counts whole calendar years. It does not account for months or the Julian-to-Gregorian change.
  • Historical dates before about the 1st century BC are often approximate.

Frequently asked questions

Is there a year 0?

No. In the BC/AD system, 1 BC is followed directly by AD 1.

How many years between 44 BC and AD 2026?

2,069 years.

Why is the answer one less than adding the numbers?

Because adding counts a year 0 that never existed.

Often used together with the BC to AD Calculator.