How these calculators work

The math behind every calculator

Every calculator on this site runs on standard, publicly documented financial formulas — not custom or hidden logic. That means the standard amortization formula for loan and mortgage calculators, the standard compound interest formula for growth and ETF calculators, and the widely used 4%-rule (25x annual expenses) guideline for FIRE-related calculators. None of this is proprietary — you could verify any of it yourself in a spreadsheet, and that's deliberate. We'd rather you trust the math because you can check it, not because we told you to.

Default assumptions

Where a calculator needs a starting assumption (like an interest rate or return rate) and you haven't entered your own, it's clearly labeled as a default and can be changed at any time. Nothing is assumed silently in the background.

The Retire Abroad quiz

The country and cost-of-living estimates in this tool are meant to be directional and educational — a starting point for thinking about where you might want to live, not a substitute for real research into visas, healthcare, tax residency, or cost of living once you've narrowed down a country. We're actively working on deepening and expanding this data over time. Treat this feature as educational and a bit of fun, not as relocation or investment advice.

How this is built and checked

RunMyWealth is built and tested by its founder against known, public financial formulas — it has not been reviewed by a licensed financial advisor, and it isn't a substitute for one. If a decision is significant (a mortgage, a major investment, a move abroad), please talk to a qualified professional alongside using these tools.

What these tools don't do

They assume simplified, constant rates of return or growth — real markets and interest rates fluctuate.

They don't account for your individual tax situation, or state/country-specific law.

They're a starting point for thinking clearly about your numbers, not personalized financial, tax, legal, or immigration advice.

See our full Disclaimer for more detail.