Calculator
Every number on this page is something you can actually test before it costs you money. That’s the whole idea behind this section — a working set of calculators for the math that actually matters when you’re building a position, sizing a trade, or figuring out whether a strategy holds up once you run real numbers through it instead of gut-checking it.
I built these because I got tired of doing the same napkin math over and over — how much compounding actually adds over 20 years versus 10, what a 2% risk limit means in actual share count, what a covered call really nets after the stock gets called away. None of it is complicated math. Most of it is arithmetic anyone learned in high school. But doing it by hand every time you want to test an assumption gets old fast, and spreadsheets have a way of accumulating errors nobody catches until the numbers stop making sense.
So these are stripped down to just the inputs that matter. No sign-up, no data collection, nothing running in the background — you type in numbers, you get an answer, and if you change your mind about an assumption you just change the number and run it again. A few of them cover ground that overlaps (compounding shows up in both the DCA calculator and the dividend reinvestment one, for instance), which is intentional — different questions call for different framing even when the underlying math rhymes.
Use these as a sanity check, not a forecast. A calculator can tell you what a 7% return compounds to. It can’t tell you whether 7% is the right assumption for your portfolio, and neither can I — that part’s still on you.
