This document describes how to build an interactive spreadsheet to calculate reinforcement bar (rebar) requirements for concrete structures. It includes sections on spreadsheet structure, formulas for calculating rebar areas, conditional formatting, and publishing. The spreadsheet contains separate worksheets to calculate requirements for local longitudinal rebars, distributed longitudinal rebars, and transverse stirrups. Conditional formatting is used to highlight cells based on whether values are below, at, or above a target value. The interactive spreadsheet can be published online for others to use.