About Calculopa

Why this site exists

Most online paycheck and mortgage calculators are national. They quietly use last year's brackets, skip state payroll programs like California SDI or Washington's WA Cares, ignore county income taxes in Maryland, and never tell you where a number came from. If you live in a state that just changed its tax law, as Georgia, South Carolina, West Virginia, Arkansas, and Utah did in 2026, a generic calculator can be wrong for most of the year.

Calculopa takes the opposite approach. Each calculator is built for one state at a time, using that state's current figures, and every page lists the primary source and the date we last verified it.

Who runs it

Calculopa is built and maintained by Zach Berling, a software engineer. It is not affiliated with any government agency, lender, insurer, or tax preparer. The site is supported by advertising (see our privacy policy), and advertisers have no influence over the calculators or the data.

What we are not

We are not accountants, attorneys, or financial advisers, and nothing here is individual tax, legal, or financial advice. The calculators are educational estimates built from public data. For decisions that matter, confirm the numbers with a licensed professional or the relevant agency. See the terms and disclaimer.

How we keep it accurate

• Figures come from primary sources: the IRS, the Social Security Administration, state revenue departments, Freddie Mac, the Census Bureau, and the Tax Foundation's compilations of state law.
• Every calculation engine is covered by automated tests that compare results to published worked examples. A change that breaks a known answer cannot be published.
• Data files carry the retrieval date and source link that you see in the "Data sources" block on each page.
• We recheck rates when agencies announce changes and at least quarterly. The data policy explains the schedule and how corrections are handled.

Found a mistake?

Please tell us. Corrections are the fastest way this site gets better. Use the contact page and include the page URL and, if you can, a link to the official figure.