A Symmetric Percentage Pricing Framework: A Bidirectional Model for Cost–Price Conversion

\textbf{Abstract.} This technical note introduces a symmetric percentage pricing framework designed to compute a selling price from a cost value using a selected percentage, and to reverse the calculation back to the exact original cost using the same percentage. Traditional markup and margin formulas rely on different bases (cost versus selling price), which results in asymmetry and prevents exact forward--reverse computation. \medskip The framework presented here resolves this inconsistency by applying a constant--ratio method that maintains perfect bidirectional reversibility. This allows users to transform cost into price and price back into cost with full mathematical accuracy using the same percentage. The method improves transparency, supports verification during audits and procurement, and simplifies price-setting tasks across retail and financial applications. \medskip The document formalizes the forward and reverse formulas, provides an illustrative worked example, and highlights the practical significance of reversible percentage computation for researchers, educators, and general users engaged in business mathematics or pricing analysis.