Fire-Calc is a small, independent project run by two cousins. This page explains who we are, how we build and test the calculators, how we write and correct our content, and how we keep the site free to use.
Who builds Fire-Calc
Fire-Calc is built and maintained by a small, independent team. We are not a large media company or a financial firm; we are a couple of people who kept running into the same problem when planning our own finances. Most calculators we found were either too simplistic to trust for a real decision or too opaque to understand what they were actually assuming. When a tool hides its assumptions, you cannot tell whether an encouraging result reflects your situation or just a generous default. We started Fire-Calc to build the tool we wanted: scenario modeling that shows its work and reflects the real tradeoffs behind a number, including contribution levels, return assumptions, account mix, taxes, and how sensitive an outcome is to the timeline you choose.
How the calculators are built and tested
Every calculator on the site runs on deterministic engines. That means the same inputs always produce the same outputs, with no hidden randomness and no server round-trip needed to compute a result. We deliberately favor transparent formulas over black-box models so that a motivated reader can follow the math on our methodology page and reproduce it by hand. To guard against silent breakage, the engines are covered by a committed parity test suite that we run before releases; it locks expected outputs for a range of scenarios so an accidental change to the math gets caught rather than shipped. Alongside those tests, our release checks run a copy review, a type check and production build, and route checks that confirm each page and redirect resolves the way we expect.
- Deterministic engines: identical inputs return identical results, and the core math runs in your browser.
- A committed parity test suite runs before releases to catch unintended changes to calculator outputs.
- Release checks add a build, type check, and route verification so broken pages are caught before deploy.
How we write and review content
We write the guides and explainer content ourselves and review each other’s work before publishing. The two of us split the work: one of us maintains the calculator engines and their parity test suite, and both of us edit the written material for accuracy and plain language. When a topic depends on numbers that change or rules that vary by person, such as contribution limits, tax brackets, or withdrawal-rate research, we point to primary sources like the IRS, the Consumer Financial Protection Bureau, and published studies rather than asking you to take our word for it. We keep a public changelog so you can see what changed and when, which matters if you saved or shared a scenario and want to know whether the underlying math has since moved. If you find something wrong, unclear, or out of date, tell us through the /contact page with the inputs you used, and we will reproduce it, fix it, and note material corrections in the changelog.
How the site makes money
Fire-Calc is free to use, and we intend to keep it that way. The site is supported by display advertising only. We do not use affiliate links, we do not earn commissions on any product, and there is no paywall or paid tier. That independence is deliberate: because we do not get paid when you choose a particular bank, broker, loan, or fund, our calculators and guides have no reason to steer you toward one. Advertising is served through standard ad slots and never changes the numbers a calculator produces.
Your privacy in short
The figures you type into a calculator, such as your income, balances, and spending, are computed in your browser and are not sent to us or stored in an account. You can use every tool anonymously and export your results locally for your own records. We do collect anonymous error and performance events through an observability endpoint so we can find and fix bugs, but that stream is about how the site is behaving, not about your financial inputs. Our Privacy Policy explains data handling and advertising cookies in full.
Educational use only
Fire-Calc is an educational planning aid, not individualized financial, investment, tax, or legal advice, and we are not licensed advisors. Treat every result as an estimate built on the assumptions you entered. Compare a conservative case against an optimistic one, stress-test the inputs that move the answer most, and confirm anything consequential with a qualified professional before you act.