Background: Cannabis excise tax structures vary widely across the states in the United States. Standardizing taxes may improve cross-state comparisons and strengthen evaluations of how taxes and prices influence public health outcomes. This study developed category-specific standardized tax metrics for flower, vaping, and edible products by incorporating price and tax structure variations using retail scanner data. Methods: We analyzed cannabis retail scanner data from dispensary point-of-sale systems for flower, vaping, and edible products in 12 states with legal recreational markets from Q1 2020 to Q4 2024. Using retail prices and excise tax policies, we converted taxes in different forms across the supply chain into standardized measures and estimated tax incidence (ratio of standardized taxes to retail prices) for each category. We also evaluated the association between standardized taxes and retail prices. Results: Mean standardized excise taxes were USD 32.58/ounce for flower, USD 180.21/ounce for vaping, and USD 0.024/milligram THC for edible products. Corresponding tax incidences were 13.03%, 13.59%, and 13.09%. Standardized taxes and tax incidences varied considerably across states. Category-specific standardized taxes strongly predicted retail prices, supporting their use as an instrumental variable candidate. Conclusions: Category-specific standardized measures of cannabis excise taxes derived from retail scanner data may support cross-state comparisons and pricing policy evaluation.