EZtol is a 1-Dimensional tolerance stackup analysis program designed to assist in understanding the impact of the accumulation of part-level dimensional variation and part-to-part assembly variation sources and the impact that they have on assembly-level requirements.

Today such analyses are performed in a spreadsheet, most commonly Microsoft® Excel®. Much work is required in creating spreadsheets that manage all of the product requirements simultaneously with consideration of common dimensions and tolerances that feed each one, properly including the impacts of the more complex geometric tolerances, and properly calculating the statistical results. Analysis spreadsheets often include a visual diagram either from the model or an assembly-level drawing to help explain the components of each of the analyses, but these too must be maintained as updates are made.