The document discusses calculating ROI for website localization. It begins by outlining the objectives and considerations for localization like expanding into new markets or improving the user experience. It then provides steps to gather key data for an ROI analysis, such as current traffic and conversion rates split by language. The document demonstrates how to use this data to estimate the incremental value and returns from localization by predicting increases in traffic, conversions, and revenues. It stresses that the analysis should be data-driven and help determine if localization is worth the total costs based on the estimated returns in the target language market.