About FreeCalculators

FreeCalculators is a free library of 934 finance, insurance, tax and business calculators plus 2,146 explanatory guides. There is no signup, no paywall and no account. Every calculator runs in your browser, and nothing you type is transmitted or stored.

Last reviewed 2026-09-04

Who writes and reviews this

Content is produced and maintained by FreeCalculators Editorial, the in-house editorial and quality-review function for this site. Its remit is narrow and specific: Sources every formula to its published definition, checks each calculator against a worked example, and re-reviews pages when the underlying rules change.

We publish under a team byline rather than invented individual personas. A named author who does not exist is a worse trust signal than an accountable team, and the accuracy claim we can actually stand behind is a process claim: the formula is sourced, the arithmetic is tested, and the page carries the date it was last checked.

Subject coverage

• personal finance
• mortgages and consumer lending
• insurance underwriting basics
• investment mathematics
• business accounting metrics
• income and payroll tax

How a calculator gets published

Each tool is a data file naming a math engine, not a bespoke page. That structure is what makes review tractable at this scale: the same engine serves many calculators, so testing the engine once covers every tool that uses it.

1. Source the formula. The definition comes from a published source — an amortization identity, an IRR definition, a statutory tax table — never from a competitor's page.
2. Implement and test the engine. Engines are pure functions with automated tests covering a benchmark case, a round-trip against a related engine, and edge conditions such as a zero interest rate or a payment below the monthly interest charge.
3. Check against a worked example. The published formula and a worked case appear on the page so you can reproduce the result by hand.
4. State the limits. Where a real quote would depend on underwriting, credit tier or jurisdiction, the page says so rather than implying the estimate is a price.
5. Re-review on change. When a rule or threshold changes, affected pages are updated and the visible “Updated” date moves with the edit — never on its own.

Sources we cite

Rules, thresholds and benchmark figures come from primary sources. Where a figure is indexed annually, the guide says so instead of freezing a number that will quietly go stale.

• Internal Revenue Service
• Consumer Financial Protection Bureau
• Federal Reserve
• Bureau of Labor Statistics
• Social Security Administration
• FDIC

What we are not

We are not a lender, broker, insurer or adviser, and we do not sell leads. Nothing here is financial, tax or legal advice. A calculator can produce a perfectly correct number and still support a bad decision, because the inputs it cannot see — your job security, your health, your other obligations — are the ones that matter most.

Some pages carry clearly labelled partner links. Those never change a calculated result, never reorder a comparison tool, and never alter the wording of a guide. See our financial disclaimer and privacy policy.

Reporting an error

If a formula, default or figure looks wrong, tell us and we will check it. Email [email protected] with the page URL and the inputs you used. A worked reference showing the number you expected gets a fix out fastest. Corrections are applied at the source and the page's update date moves with them.

Full contact details are on the contact page.

What is covered

Browse everything from all calculators or all guides.