About MoneySims
MoneySims is a free library of interactive money simulators — compound interest, retirement survival odds, options payoffs, tax brackets, debt payoff. No signup, no paywall, no email capture. You move the sliders, the math runs in your browser, you see the result.
What this is
Every tool here is a small, purpose-built simulator for one question: what does an extra $200/month actually do to a 401(k) over 30 years? What's the real survival rate of a 4% withdrawal rate against historical-style market sequences? What does a covered call actually pay off, at every price, at expiration? Each simulator states its assumptions on the page, next to the result — not buried in a footnote.
Who it's for
People who want to check the math themselves. Maybe you heard a claim in a video, a podcast, or from a coworker, and want to see what happens when you plug in your own numbers instead of theirs. MoneySims doesn't tell you what to do with your money — it shows you the arithmetic and lets you draw your own conclusion.
The YouTube connection
MoneySims is the companion tool set for The Compounding Desk and related channels. When a video shows a chart or a result — a retirement Monte Carlo run, a debt payoff timeline, a tax bracket breakdown — it links to the exact scenario used on screen. Follow the link, and the simulator loads with the same inputs, so you can rerun it, change an assumption, and see how sensitive the conclusion really is. No re-typing numbers from a paused video.
Be honest with yourself about these numbers
- Every tool lists its assumptions in plain language, on the page, next to the result.
- The models are simplified on purpose — real markets, real tax code, and real life are messier than any calculator.
- This is educational software. Nothing here is financial, tax, or investment advice, and no output is a prediction or a recommendation.
- There are no accounts. Simulations run entirely in your browser — the numbers you enter are never sent anywhere. We collect anonymous usage stats (which tools get used, which videos send visitors) with no cookies and no personal data.
See Methodology for how the simulators are actually built, including how the random-market tools stay reproducible.