Guesstimate

What Guesstimate is

Guesstimate is a web spreadsheet for building models and forecasts when quantities are uncertain. A cell can contain a confidence interval or a dataset, and calculations that depend on it account for that uncertainty. For stochastic expressions, the product uses Monte Carlo sampling with 5,000 samples per expression. Analysis Mode presents sensitivity plots to show which inputs affect an output. You can also turn selected inputs into a calculator form and have it display selected outputs calculated from the model. Financial functions include NPV, ROI and WACC, using Finance.js.

The free plan lets users create unlimited public models. Anyone can view a public model, but only its owner can save edits; changes made while viewing another person’s model can be edited locally but are not saved. Paid plans include private models for individuals and organizations, with organizational models visible within their 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. Its maker says small companies most commonly use it for cost estimation and forecasting.

Who it suits

Guesstimate suits people modeling uncertain quantities, including small companies doing cost estimation and forecasting. It can also suit users who want to examine input sensitivity or turn model inputs into a calculator form.

Limits

The free plan allows unlimited public models, but anyone can view them and only the owner can save edits. Private models for individuals and organizations are available on paid plans.

Getting started

1. Open https://www.getguesstimate.com/ in a web browser.
2. Create a public model for free.
3. Use a confidence interval or dataset for an uncertain input.
4. Use Analysis Mode to view sensitivity plots, or select inputs and outputs for a calculator form.
5. Choose a paid plan for private individual or organizational models.
6. Use the repository instructions to run the open-source application locally.

Verdict

Choose Guesstimate to model uncertain quantities in a web spreadsheet, with uncertainty-aware calculations, sensitivity plots and calculator forms. Its free plan supports unlimited public models; look elsewhere if you need private models without a paid plan or need to save edits to someone else’s public model.