The INTCAL98 radiocarbon calibration curve covers the period 24,000–0 cal BP, integrating data from tree rings, corals, and marine sediments. The curve is constructed by converting radiocarbon (¹⁴C) ages into calibrated (cal) ages, accounting for variations in ¹⁴C levels in the atmosphere and oceans. The calibration process involves comparing ¹⁴C ages from different sources, such as tree rings and corals, and adjusting for regional and temporal differences. The curve includes corrections for marine reservoir effects, which account for the difference between atmospheric and oceanic ¹⁴C levels. The calibration curve is based on a combination of decadal and single-year data, with adjustments made to account for variability in ¹⁴C levels over time. The curve also incorporates data from marine varve chronologies to extend the calibration range. The INTCAL98 curve is used to convert radiocarbon ages into calibrated ages, with uncertainties accounted for in the standard deviation. The curve is validated against various data sources, including coral and varve data, and is used for age calibration in a wide range of scientific disciplines. The calibration curve is available for download from the Quaternary Isotope Laboratory web site.The INTCAL98 radiocarbon calibration curve covers the period 24,000–0 cal BP, integrating data from tree rings, corals, and marine sediments. The curve is constructed by converting radiocarbon (¹⁴C) ages into calibrated (cal) ages, accounting for variations in ¹⁴C levels in the atmosphere and oceans. The calibration process involves comparing ¹⁴C ages from different sources, such as tree rings and corals, and adjusting for regional and temporal differences. The curve includes corrections for marine reservoir effects, which account for the difference between atmospheric and oceanic ¹⁴C levels. The calibration curve is based on a combination of decadal and single-year data, with adjustments made to account for variability in ¹⁴C levels over time. The curve also incorporates data from marine varve chronologies to extend the calibration range. The INTCAL98 curve is used to convert radiocarbon ages into calibrated ages, with uncertainties accounted for in the standard deviation. The curve is validated against various data sources, including coral and varve data, and is used for age calibration in a wide range of scientific disciplines. The calibration curve is available for download from the Quaternary Isotope Laboratory web site.