About Zetta Calculators
Free, fast, no-fluff online calculators. Built so you can get a number, understand how it was reached, and move on with your day.
What this site is
Zetta Calculators is a library of free online calculators covering finance, health, math, conversions, real estate, sports, education, and more. Every calculator on the site is free to use, requires no login, and runs in your browser — your inputs never leave your device.
Alongside the calculators we publish long-form articles that explain the formulas, real-world context, and the assumptions behind the math. The goal is for you to leave each page with both an answer and an understanding of why the answer is what it is — because a number you can defend is more useful than a number you just trust.
Who it's for
- Homebuyers and renters running scenarios on mortgage payments, rental yield, and property taxes
- Students double-checking algebra and geometry homework, calculating GPAs, planning final-exam strategy
- Athletes and fitness enthusiasts calibrating training paces, BMI, BMR, and heart rate zones
- Small business owners sizing markup, margin, breakeven, and ROI
- Travelers and cooks needing quick conversions between metric and imperial units
- Professionals who want a sanity check before a meeting or a client call
Our principles
- Free, always. No paywall, no premium tier, no "calculator unlocked when you sign up." If you can reach a calculator URL on the site, it works.
- Privacy first. Inputs are processed in the browser. We don't log what you calculate or correlate it with you. The most we collect is anonymized analytics about which pages were visited.
- Show the work. Each calculator includes the formula, an explanation, and a worked example. We treat readers as adults who can handle math, not click-bait.
- U.S. defaults, global usability. Where conventions differ (tax rates, date formats, unit systems), we default to U.S. but support other regions where it matters.
- No "guesstimates" pretending to be answers. If a calculator depends on assumptions, those assumptions are listed. If they don't apply to your situation, the result won't either.
How we make the calculators
Each calculator is built from a documented formula, hand-coded JavaScript that runs entirely client-side, and a content layer that explains the formula and walks through a sample. Where the math has multiple accepted variants (Tanaka vs Karvonen for heart rate zones, Riegel vs Cameron for race-time prediction, etc.) we pick the version most commonly used in the field and explain why.
We don't use the term "AI calculator" — every calculator is a deterministic function. The same inputs always produce the same outputs, and if you check the math by hand you'll get the same number we display.
Editorial process
Articles are reviewed against primary sources — peer-reviewed papers for science topics, IRS publications for tax topics, NAR data for real estate, USATF age-grading tables for running. When numbers in an article come from a specific data source, the source is named in the body. We update articles when underlying data changes (e.g., tax brackets, conforming loan limits, age-grade tables).
Mistakes
If you spot a calculation error, a typo, or out-of-date guidance, please tell us. We will fix it and credit you (only if you want to be named).
Contact
For partnership requests, calculator suggestions, corrections, or anything else: our contact form or email hello@zettacalculators.com.
Last updated: April 28, 2026