About KnownSum
Free US tax and money calculators that show their working.
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 built and maintained by Muhammad Adeel. I write the calculators, check them against the published rules, and update them when the rules change.
How the figures are checked
- Every tax figure lives in a single data file and is traced to published IRS guidance.
- Each page shows the date its figures were last verified.
- Figures are re-checked against the source at the start of every tax year, and whenever the IRS changes them.
Read the detail on the methodology page and see every reference on the sources 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.
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.