About Zetta Calculators

Free calculators for math, school and dates, each with the formula, a worked example and its sources, so you can check the answer yourself.

What this site is

Zetta Calculators is a library of free online calculators and the guides that explain them. The main focus is math, education and date and time: fractions and percentages, GPAs and final grades, square roots and slopes, the number of days or working days between two dates. Every calculator is free, needs no account and runs in your browser.

Each updated calculator page shows the formula it uses, works through an example step by step, says what the tool does not do and lists the sources it relies on. The aim is that you leave with an answer you can check by hand, not just a number to trust.

Who runs it

Zetta Calculators is run by Sunit Kumar, the founder and editor, who comes from a software-development background. Sunit builds the calculators and is responsible for every calculator and guide on the site. You can also find Sunit on LinkedIn.

How the pages are made

Since October 2026 every calculator we update follows the same process: the formula comes from a primary source, every number in its worked examples is produced by the calculator itself, and the tool is tested against answers known in advance before the update goes live. We started with the math, education and date calculators and are working through the rest. The details are in two pages:

Editorial policy: which sources we use, how examples are checked, how pages are updated and how corrections are handled.
How we test our calculators: the test process, how edge cases and rounding are handled, and a dated log of the errors we have found and fixed.

Principles

Free, with no sign-up. Every calculator works without an account or a paywall.
Your inputs stay on your device. The calculations run in your browser, and the numbers you type are not sent to us. We use Google Analytics to count page visits; the privacy policy has the details.
No ads, no affiliate links, no sponsored content. Nobody pays to appear on a page or to influence a result.
Show the work. Updated pages carry the formula, a worked example and the sources, so you can follow how the answer was reached.
Say what a tool does not do. When a result depends on an assumption or has limits, the page says so. When an input makes no sense, an updated calculator gives no result and says why, rather than showing a wrong number.

Mistakes and suggestions

If you find a wrong result, an error in a guide or something out of date, please tell us. Confirmed errors are fixed and recorded in the corrections log.

The calculators are for education and everyday planning. They are not financial, medical, legal or tax advice; see the disclaimer.

Contact

For corrections, calculator suggestions or anything else, use the contact form or email hello@zettacalculators.com.

Last updated: October 16, 2026