How we build & verify our tools

Formula selection

Every calculator implements a published, well-established formula, drawn from textbooks, official standards bodies (NIST, ISO, IEEE), peer-reviewed sources, or jurisdictional rule-sets (IRS, HMRC, etc. for tax tools). When a tool exposes a formula in its "How it works" section, that is the exact mathematical expression being executed.

For tools that aggregate multiple methods (e.g. retirement projections), we default to the most widely accepted approach and document the assumptions on the tool page itself.

Verification

Each calculator is verified against known canonical inputs before release. Where official reference implementations exist (e.g. IRS tax tables, NIST unit definitions, mortgage amortization examples from authoritative finance texts), our outputs match to the documented precision.

Numerical results are computed in JavaScript inside your browser. No values are transmitted to a server, so identical inputs always produce identical outputs.

Update cadence

Every tool shows a "Last reviewed" date directly under its title. We re-check tools whenever:

• The underlying standard, rate, or regulation changes (e.g. annual tax brackets, currency reference rates).
• A user reports an issue via the in-page feedback button.
• An internal audit flags a tool as overdue based on its category's typical refresh cycle.

Transparency

Each tool's "How it works" section shows the formula, the variables, a worked example, and any assumptions or notes. If you need to inspect the calculation itself, every result is computed in client-side JavaScript that runs in your browser, and you can view it with your browser's developer tools.

Disclaimer on regulated topics

Tools in categories like finance, taxes, medicine, insurance, and real estate produce accurate calculations for the inputs you provide, but should not be the sole basis for consequential decisions.

Tax brackets, mortgage qualification, medication dosing, insurance premiums, and similar regulated calculations depend on individual circumstances that no general-purpose tool can fully capture. For decisions that matter, verify ExaCalc's output with a qualified professional (accountant, doctor, insurance broker, financial advisor) who can apply your full context.

Report an issue or suggest an improvement

The fastest way to flag a problem or request a change is the floating Feedback button at the bottom-right of every tool page. It captures the tool, your suggestion, and (optionally) your email so we can follow up.

You can also reach us via the Contact page.