About WhatIf Labo

Simulate before you decide.

whatiflabo.com is a collection of free what-if simulators. Change one assumption, see how the result moves, and do it before the decision is real. Every tool runs entirely in your browser, so what you type never leaves your device.

We believe that financial anxiety often comes from not being able to see the future clearly. Our simulators let you explore "what if" scenarios — what if I invest this instead of spending it? What if I rent instead of buy? What if I retire early?

Our principles

• Data stays with you — All calculations happen in your browser. We don't have servers that see your financial data.
• No signup required — Use any tool immediately, no account needed.
• Plain language — We explain financial concepts in words everyone can understand.
• Formulas you can check: every result has a "how it's calculated" section, the calculations have unit tests, and the source code is on GitHub.
• Free forever — Core tools will always be free.

What's here

• Life Lab: money, career, health, family, housing and more, in 20 topic areas. You can keep a profile and snapshots, so the tools remember your numbers and show how they change over time.
• Dev Lab (English only): developer utilities such as a JSON formatter, regex tester and cron explainer, each built on the real spec.

Contact

Questions, corrections or tool ideas: [email protected]. What to include when reporting a wrong number is on the contact page.

Built with Astro, SolidJS, and a lot of care.