Free calculators, built and checked by a real person
71 calculators, no sign-up, and every formula written down and sourced — not a black box.
Irvin Abarca
Founder & Editor, Ezcalcus · Page last updated September 20, 2026Irvin Abarca founded Ezcalcus to build fast, free, ad-supported calculators for the everyday financial, health, and household math people actually search for. Every calculator on this site is built from a documented, publicly verifiable formula, cross-checked against the source it's based on, and reviewed before publishing — no calculator ships without a written explanation of exactly how its numbers are produced.
Why Ezcalcus exists
Most calculator sites either bury the formula behind a wall of ads or don’t explain their math at all. Ezcalcus is built the other way around: every calculator has a written explanation of exactly what it computes and why, right on the same page as the tool itself, along with worked examples and a sources section pointing to where the formula or guideline actually comes from.
How each calculator is built and reviewed
Every calculator starts from a documented, publicly verifiable formula — things like the Mifflin–St Jeor equation for calorie needs, the standard loan amortization formula, the IRS’s published marginal tax brackets, or the National Weather Service’s wind chill and heat index regressions. Formulas are implemented once as shared, reusable logic and checked against known reference values before a calculator is published, so the same math isn’t re-derived (and re-risked) for every tool.
Each calculator page shows a “Reviewed by” byline with the date it was last substantively reviewed, and a sources section linking to the authoritative body its formula or guideline is based on. Estimates that depend on individual factors the calculator can’t know — like exact state tax rates, personal metabolism, or your specific lender’s fees — are labeled as estimates, not guarantees.
What Ezcalcus is not
These calculators are educational tools, not financial, medical, or legal advice. Results are estimates based on the inputs you provide and the general formula each tool uses — they don’t know your full financial picture, medical history, or local regulations. For decisions that matter — a mortgage, a tax filing, a medical concern — verify against a professional or the primary source linked on that calculator’s page.
Corrections and feedback
Spotted a formula that looks wrong, an outdated figure, or a bug? That’s useful — email contact@ezcalcus.com or visit the Contact page. Corrections are investigated against the cited source and the page’s last-updated date is bumped whenever a calculator’s logic or content changes.