From Rows to Reasoning: A Retrieval-Augmented Multimodal Framework for Spreadsheet Understanding

Large Language Models (LLMs) struggle to reason over large-scale enterprise spreadsheets containing thousands of numeric rows, multiple linked sheets, and embedded visual content such as charts and receipts. Prior state-of-the-art spreadsheet reasoning approaches typically rely on single-sheet compression or full-context encoding, which limits scalability and fails to reflect how real users interact with complex, multimodal workbooks. We introduce FRTR-Bench, the first large-scale benchmark for multimodal spreadsheet reasoning, comprising 30 enterprise-grade Excel workbooks spanning nearly four million cells and more than 50 embedded images. To address these challenges, we present From Rows to Reasoning (FRTR), an advanced, multimodal retrieval-augmented generation framework that decomposes Excel workbooks into granular row, column, and block embeddings, employs hybrid lexical-dense retrieval with Reciprocal Rank Fusion (RRF), and integrates multimodal embeddings to reason over both numerical and visual information. We tested FRTR on six LLMs, achieving 74% answer accuracy on FRTR-Bench with Claude Sonnet 4.5. On the enterprise-scale, multi-sheet workbooks in FRTR-Bench, FRTR improves over the best existing baseline by 50 percentage points (74% vs. 24%). On the single-sheet SpreadsheetLLM benchmark, FRTR achieves comparable accuracy (87% with GPT-5 vs. 90% for SpreadsheetLLM) while reducing token usage by roughly 50% compared to direct serialization methods.