About Beyond Napkin Math

Beyond Napkin Math builds free, easy-to-use calculators for big money decisions, like buying a rental property or planning for retirement. Our aim is simple: give you clear answers and show exactly how we got there, so you can decide with confidence.

How the tools are built

• Every assumption is visible and editable. Defaults are starting points from published figures and typical ranges, never hidden constants.
• The math is explained. Each tool has a methodology page covering how it calculates and what it leaves out.
• Official figures are kept current. Tax limits and benefit formulas are listed, with sources, on Sources and updates and reviewed every year.
• They go beyond rough rules of thumb. Stress tests, tax effects and timing are built in, because those are what change the answer.

Free, with no sign-up

Every tool is free and works without an account. Your inputs are saved in your own browser so you can come back to them; see the privacy policy for details.

Educational use only

The tools are educational and are not financial, tax or legal advice. See the terms of use.