Disclaimer

Education only, not financial advice. Doubling Time explains how money math works. It doesn't tell you what to buy, sell, or do. Check your own numbers and terms before you decide anything.

Not advice

Doubling Time is not a financial adviser, broker, or tax professional. Nothing on this site is an offer or solicitation of any kind, or a recommendation of any product, account or strategy.

Estimates, not promises

Results are estimates from the formulas shown on each page. They depend entirely on the inputs and assumptions you use. Real accounts have fees, taxes, changing rates and rules that a simple calculator leaves out.

Hypothetical. Results assume the same rate every year. Real returns jump around and can be negative. Fees, taxes and inflation are ignored unless you add them. Past returns don't predict future returns.

Illustration. Assumes no new charges, no fees and no rate changes unless you enter them. Your lender's statement and terms are the real numbers.

Simplified. Federal income tax only, single filer, standard deduction, no credits, 2026 figures. State and local taxes are not included.

Rates and data

Rates and limits are as of the dates shown (currently: Fed G.19 Sep 8, 2026 release, FDIC Sep 21, 2026, IRS 2026 tax year (checked Sep 28, 2026), student loans loans first disbursed Jul 1, 2026 - Jun 30, 2027) and may be outdated when you read this. Historical S&P 500 returns come from A. Damodaran (NYU Stern); inflation data from the U.S. Bureau of Labor Statistics. We check our numbers, but we can't promise every figure is accurate or current.

Affiliate links

We don't use affiliate links.

Ads

We may show ads in the future. Advertisers don't influence our math or what we show.

Last updated Sep 28, 2026.