What FounderCalc is
FounderCalc is a free collection of business calculators for indie founders, freelancers and early-stage SaaS builders — the questions that come up constantly when you run a small digital business and need an accurate answer in ten seconds rather than a spreadsheet in twenty minutes.
Every calculator covers one specific question: what Stripe actually pays out on a $2,400 invoice, how many months of runway a given burn rate buys, what hourly rate a $95,000 income target implies once non-billable time and self-employment tax are accounted for. Each tool sits alongside a written explanation of the formula it uses, the assumptions behind it, and the benchmarks that make the result meaningful.
Who publishes it
FounderCalc is written and maintained by Guillaume Malvestio, a software developer registered as a sole trader in France. It is an independent, one-person project, not a company blog or a content network — full publisher details are on the legal notice page, as French law requires.
The site is not backed by, affiliated with, or endorsed by Stripe, PayPal, Shopify or any other company whose pricing it covers. Where a page links to a paid product as an affiliate, that link is labelled as such on the page.
How the numbers are produced
Formulas. Every calculator implements a standard, publicly documented formula — the same arithmetic used in accounting texts, investor updates and SaaS operating handbooks. Where a metric has more than one accepted definition (LTV computed on revenue versus gross profit, churn measured by logo versus revenue), the page states which one the tool uses and why the distinction matters.
Rates and fees. Processor fees, tax rates and similar third-party figures are taken from each provider's own published pricing page, and the page links back to that source so you can confirm the current figure yourself. Worked examples are computed at build time from the same rate constants the calculator uses, so an example can never drift out of sync with the rate quoted next to it.
Benchmarks. Figures described as typical or healthy — a 3:1 LTV:CAC ratio, 25–40% employer on-costs, 50–70% freelance utilisation — are widely used industry rules of thumb, presented as ranges rather than targets. They are context for reading your own number, not standards your business is failing to meet.
Corrections. Third-party pricing changes, and mistakes happen. If a figure on this site is wrong or out of date, tell me and it gets fixed; corrections are treated as a priority over new tools.
What the results are not
Calculator output on this site is information, not advice. Nothing here is financial, tax, accounting, investment or legal advice, and none of it accounts for the specifics of your jurisdiction, your entity type or your circumstances.
Tax and payroll tools in particular are planning estimates: rates, thresholds and allowances differ by country and change between tax years. Use them to decide how much to set aside, then confirm the actual liability with your accountant or tax authority before you file anything. Valuation and investment models are only as reliable as the forecasts you feed them — treat their output as one input to a decision, not the decision. The full position is in the Terms of Use.
Your data stays in your browser
Every calculator runs entirely as client-side JavaScript. The numbers you type are processed in your browser and are never transmitted to this site or anywhere else — there is no account, no login, and no analytics script recording what you enter. The only request your browser makes is the ordinary one for the page itself.
That is a structural property of how the site is built rather than a promise about how data is handled after collection: there is no server-side calculation, so there is nothing to collect. What little data does get processed — server logs, and the advertising described in the privacy policy — is set out there in full.
Why it exists
These calculations are not difficult. Doing them from scratch every time is friction, and friction is why founders guess at numbers they could know. A single-purpose page that opens instantly, works without an account, explains its own formula and remembers nothing about you removes that friction — and costs nothing to keep running, which is why it can stay free.
The site is funded by advertising. It has no paid tier, sells no data, and gates no calculator behind an email address.
Suggestions and corrections
If a calculator you need is missing, a result looks wrong, or an explanation is unclear, the contact page is the place to say so. Tool suggestions from people actually running businesses are where most of this suite came from.