RCYBP - Radio Carbon Years Before the Present

How and Why Radiocarbon Dates are Calibrated

RCYBP stands for Radio Carbon Years Before the Present, although it is abbreviated in many different ways. It is a shorthand reference to the uncalibrated date recovered from carbon 14 dating. In brief, radiocarbon dating compares the amount of c14 in a dead animal or plant to the available carbon in the atmosphere. (See the glossary entry for more details). But, carbon in the atmosphere has fluctuated over time, and so raw RCYBP dates must be calibrated to a more accurate time value.

In general, radiocarbon dates can be calibrated by using comparable dendrochronological dates or other known dating systems. Numerous software programs have been developed to complete the calibrations for the investigator, including a new online version of the best known software CALIB. Calibrated dates are typically listed in publications with the word "cal" after it.

The correction data for calibrating RCYBP dates is derived from available dendrochronological records within a given region, a fact which has spurred the extension of tree ring research. The latest information about available correction dates is published in the journal Radiocarbon and available for download in a free file called IntCal09 Supplemental Data.

Common Abbreviations for RCYBP: C14 ka BP, 14C ka BP, 14C ka BP, radiocarbon years, c14 years before the present, rcbp, carbon-14 years before the present, CYBP

Common Abbreviations for Calibrated Dates: cal BP, cal yr. B.P.


Read more about the Radiocarbon Revolution, part of the Timing is Everything short course on archaeological dating. Also, see the online calculator called CALIB; the original program was developed by Minze Stuiver and colleagues over 20 years ago and is probably the best known.

Also see the glossary entry for cal BP for additional information about how dates are calibrated.

Reimer, P., et al. 2009 IntCal09 and Marine09 radiocarbon age calibration curves, 0-50,000 years cal BP. Radiocarbon 51(4):1111-1150.

Reimer, Paula J. et al. 2004. IntCal04: Calibration Issue. Radiocarbon 46(3).

Stuiver, Minze and Bernd Becker 1986 High-precision decadal calibration of the radiocarbon time scale, AD 1950-2500 BC. Radiocarbon 28:863-910.

Stuiver, Minze and Gordon W. Pearson 1986 High-precision calibration of the radiocarbon time scale, AD 1950-500 BC. Radiocarbon 28:805-838.

Stuiver, Minze and Paula J. Reimer 1993 CALIB User's Guide Rev. 3.0. Quaternary Research Center AK-60, University of Washington.

This glossary entry is part of the Dictionary of Archaeology.