About KnownSum

What this site is

KnownSum is a directory of calculators for everyday US tax and money questions: what you owe, what you keep, and what you can claim. Every calculator shows the steps behind its answer, so you can check the result rather than take it on trust.

Who runs it

KnownSum is run by a small independent editorial team. We write every calculator, check each figure against its official source, and update the pages when the rules change.

How the figures are checked

• Official sources only. Every rate, cap, threshold and fee comes from the body that sets it: the IRS for federal tax, a state's tax or motor vehicle agency for vehicle taxes and fees, the statute where one applies, and Fannie Mae, Freddie Mac and the CFPB for mortgage rules. Lender terms come from each lender's own pages. Other calculator sites are never used as a source.
• Dated verification. Each page shows the date its figures were last checked against the source, and every source is listed with that date on the sources page. Where a figure could not be confirmed from an official source, the page says so instead of estimating it.

Read how each calculation works on the methodology page.

Your data stays with you

Calculations run in your browser. What you type into a calculator is not uploaded, stored or shared. The calculators are free to use.

Advertising and analytics

The calculator pages show one advertisement from Adsterra, below the content, and the site uses Google Analytics to count visits. These services may set cookies or collect standard browser information. They never receive the numbers you type into a calculator. See the privacy policy for details.

What this site is not

KnownSum provides general information, not tax advice. The results are estimates based on the stated rules and the inputs you give. For advice on your own return, speak to a qualified tax professional.

Get in touch

Spotted a mistake or have a suggestion? See the contact page.