The Composite Burn Index (CBI) is a field measure of burn severity. It captures the magnitude of ecological change on a site by rating many factors on a 30meter plot and then integrating those factors to generate an estimate of burn severity. The strength of CBI depends on many interpretations of how fire altered a site, rather than hard quantitative measures or a high degree of precision for any one rating factor. It has been extensively used in many different ecosystems in the United States to calibrate dNBR, a meso-scale remote sensing index of burn severity, for levels of burn severity and measure strength of association between ground severity and the remote sensing index. This talk will provide an overview of the CBI and its use for calibrating and assessing accuracy of dNBR.