The CALIB 3.0 program is an updated version of the radiocarbon age calibration program, incorporating new data and refinements. It provides a calibration of radiocarbon (¹⁴C) ages to calendar years, including Δ¹⁴C series and probability distributions. The program is menu-driven and can be used on IBM-compatible computers. A Macintosh version is available upon request. The program uses a combination of tree-ring data, marine data, and atmospheric data to create a calibration curve covering nearly 22,000 calendar years (approximately 18,400 ¹⁴C years). The data sets used in the program are based on a 6-year calibration effort by several laboratories (1986–1992). The program includes corrections to previously used data sets and incorporates new data for the 1993 version. The calibration data sets include bidecadal and decadal data for tree rings, marine data for bidecadal models, and atmospheric data for samples older than 10,100 ¹⁴C years. The program also includes a smoothing spline for atmospheric data and allows for the calculation of probability distributions for radiocarbon ages. The program can be used to check the consistency of multiple ¹⁴C ages using a χ² test. The CALIB 3.0 program provides a range of outputs, including calibrated age ranges, probability distributions, and calibration curves. The program is designed to be used by researchers and archaeologists to calibrate radiocarbon dates to calendar years. The program is available from the Quaternary Isotope Laboratory and is described in detail in the CALIB User's Guide. The program is also referenced in several scientific publications.The CALIB 3.0 program is an updated version of the radiocarbon age calibration program, incorporating new data and refinements. It provides a calibration of radiocarbon (¹⁴C) ages to calendar years, including Δ¹⁴C series and probability distributions. The program is menu-driven and can be used on IBM-compatible computers. A Macintosh version is available upon request. The program uses a combination of tree-ring data, marine data, and atmospheric data to create a calibration curve covering nearly 22,000 calendar years (approximately 18,400 ¹⁴C years). The data sets used in the program are based on a 6-year calibration effort by several laboratories (1986–1992). The program includes corrections to previously used data sets and incorporates new data for the 1993 version. The calibration data sets include bidecadal and decadal data for tree rings, marine data for bidecadal models, and atmospheric data for samples older than 10,100 ¹⁴C years. The program also includes a smoothing spline for atmospheric data and allows for the calculation of probability distributions for radiocarbon ages. The program can be used to check the consistency of multiple ¹⁴C ages using a χ² test. The CALIB 3.0 program provides a range of outputs, including calibrated age ranges, probability distributions, and calibration curves. The program is designed to be used by researchers and archaeologists to calibrate radiocarbon dates to calendar years. The program is available from the Quaternary Isotope Laboratory and is described in detail in the CALIB User's Guide. The program is also referenced in several scientific publications.