About

A growing collection of hard Excel formula challenges. Each problem is solvable in a single cell using modern Excel — LET, LAMBDA, REDUCE, SCAN, MAP, MAKEARRAY, and friends.

The rules:

• Pure formulas — no VBA, no macros, no Power Query.
• One formula in one cell — no helper columns or intermediate cells.
• Modern Excel only (Microsoft 365 / Excel 2024+).

Type your output value into the checker on each challenge page. Progress is saved locally in your browser.