Understand the numbers behind financial independence.

Who is responsible for FourPercent?

FourPercent is developed and maintained by Stian, the developer publishing as stianlab. The project repository contains the calculator source, tests and change history.

Stian is responsible for the site’s development and maintenance. Calculation conventions, sources and limitations are published alongside the tools. Financial qualifications or professional review are not claimed. Questions and corrections can be sent to [email protected].

What we publish

Our focus is the connection between spending, savings and the point when investments might cover living costs. The tools let you compare assumptions, inspect the calculation and test a retirement plan against uneven returns.

Stian publishes and maintains FourPercent. We do not present the calculations as a professional review of your finances, and do not claim an independent financial adviser has approved your plan.

How to check our work

The methodology page explains return conventions, cash-flow timing and model boundaries. Worked examples on the main calculators give inputs and numerical results you can reproduce. The historical test provides a downloadable dataset and its source.

Automated checks cover compounding, the timing of the FIRE target, Coast FIRE thresholds, inflation adjustment and withdrawals that exhaust a portfolio exactly. These checks establish consistency with the stated model; they cannot establish whether future investment assumptions will hold.

Corrections and feedback

Send corrections to [email protected]. Include the page, currency, inputs, result and what you expected. You can use fictional numbers; do not send account numbers or financial documents.

Changes to a model or data source are described on the affected page. For dated tax and market information, check the source and reference year before relying on the result.

How the site is funded

We intend to support the free tools with advertising. Advertising availability depends on the provider’s approval. Ads are separate from calculation results and do not change the formulas. The privacy page describes browser storage and optional analytics.

Start with your question

When might I reach financial independence?
How could my savings grow?
When might retirement contributions become optional?

How we build and check the tools

FourPercent is an independent calculator project. We use AI assistance in code and explanatory drafts, publish calculation conventions and link financial rules to their original sources. Automated checks compare formulas with known examples and test edge cases; browser checks cover the user-facing results.

We do not claim a certified financial author, professional tax review or an independent audit. Our original model comparisons include inputs and downloadable results so readers can inspect the work. The method and content history describes material changes, including the 5 October 2026 example review. Contact the address above to report a reproducible error.