About KindCalc

KindCalc is a small library of U.S.-focused calculators: paychecks by state, mortgages, refinance break-even, credit card payoff, amortization, tips, percentages, BMI, dates, units, time zones, GPA, writing stats, passwords, color contrast, and QR codes. There are 31 tools in this wave. Each page is a working calculator plus an explanation of the formula, examples, and limits.

We built the site because search results for simple math are crowded with pages that hide the tool under pop-ups or ship your inputs to a server. Every KindCalc calculator runs in your browser. We do not need your salary, birth date, or draft essay to show you a number.

The project is operated as a useful, ad-supported site. After Google AdSense approval, pages may show a small number of ads placed away from buttons and results. Ads should never be the product. If a page is wrong, tell us.

KindCalc is not a bank, tax preparer, university registrar, or clinic. Money and health tools include disclaimers because a clean formula is still not advice about your life.

Sources we cite on the tools

Paycheck federal brackets and 401(k) limits follow IRS figures for the 2026 tax year as published when those pages were written. Inflation uses annual-average CPI-U (U.S. city average, 1982–84 = 100) from the Bureau of Labor Statistics, via the Minneapolis Fed CPI table; 2026 is labeled as their estimate until a full annual average exists. House affordability uses common 28/36 and 31/43 DTI planning ratios—not a specific lender’s overlay. Credit card minimums on the payoff page are a CARD Act-style sketch (interest plus 1% of principal, $35 floor), not a specific issuer’s contract. Refinance math is principal and interest plus the closing-cost field you enter—not a lender’s APR with every prepaid item. Sales tax by state is a state rate plus an average local add-on, not a live zip-code lookup. If a figure on a page is stale, tell us.