About Everyday Math Calculators

Last updated June 5, 2026

Percent, tip, sales tax, markup — the arithmetic everyone does and nobody enjoys double-checking. I built fast, transparent versions that show the working so you can trust the number.

What’s on this site

Right now there are 8 calculators here: Percentage Calculator, Tip Calculator, Sales Tax Calculator, Discount Calculator, Unit Price Calculator, Time Card Calculator, Hourly to Salary Calculator, and Markup & Margin Calculator. Each one is a single-purpose tool that shows its formula, lists its assumptions, and runs on any device with no signup.

Why these are different

Most calculator sites hand you a number and hide the formula. Every tool here does the opposite: the exact formula, the assumptions, and a worked example are shown right on the page, so you can check the result instead of trusting it blindly. There’s no account, no paywall, and no signup.

How the math is kept honest

Each formula is shown in full and was independently re-derived and spot-checked against the calculator’s code. Reference values (typical rates, averages, rules of thumb) are labeled as approximate and are editable, so you can put in your own real numbers. These tools do everyday arithmetic for convenience; for tax, payroll, or legal figures that must be exact, confirm with the relevant authority or professional.

Found a mistake?

I’d genuinely like to know. Email [email protected] and I’ll fix it.