To date, an openly available and well-described cost estimation model with Functional Size Metrics (FSMs) does not exist. The most common methods used to estimate effort with FSMs in research papers is to perform linear or nonlinear regressions. These research papers do not account for additional effort factors and their effects on development effort. Another suggested method is to convert FPs to SLOC and use existing cost models - a option provided by COCOMO(R) II. However, the conversion between FPs and SLOC assumes that both size metrics grow in a similar manner and thus, additional estimation errors can be introduced in the estimation process. This presentation goes over the work I did to calibrate the COCOMO(R) II model to use either IFPUG Function Points (FPs) or COSMIC Function Points (CFPs) directly as size parameters. The calibrated COCOMO(R) II model estimated within 25% of the actuals 68% of the time for FPs (as in, PRED(25)=68%) and 70% of the time for CFPs (PRED(25)=70%).