Guesstimate

What Guesstimate is

Guesstimate is a web spreadsheet for modeling and forecasting quantities that are uncertain. Cells can contain confidence intervals or datasets, and calculations that depend on them carry that uncertainty forward. For stochastic expressions, the tool uses Monte Carlo sampling with 5,000 samples per expression. Analysis Mode shows sensitivity plots to help identify which inputs affect an output. Selected model inputs can also be presented as a calculator form, with chosen outputs displayed from the model. Financial functions include NPV, ROI, and WACC, using Finance.js. Users can create unlimited public models for free. Anyone can view those models, but only the owner can save edits; changes made while viewing someone else’s model are local and are not saved. Paid plans provide private models for individuals and organizations, with organizational models visible within the owning organization. The application code is open source, and its repository includes instructions for running it locally. QURI, a nonprofit research organization, says it maintains Guesstimate. The maker says small companies most commonly use it for cost estimation and forecasting.