Spreadsheets & Calculators
Tools that show their work.
Free spreadsheets built on the same arithmetic as the essays. No signup, no email, no macros.
Most personal finance calculators hand you a number and hide the formula. That is backwards. A projection is only as good as the assumptions underneath it, and if you cannot see them, you cannot argue with them. Every sheet here puts its assumptions in labeled cells you can edit, and every result is a live formula rather than a figure typed in by hand.
They are plain .xlsx files. They open in Excel, Numbers, LibreOffice, and Google Sheets. Nothing runs, nothing phones home, and nothing asks for your email address.
Available now
11 toolsNewest first. More on the way, roughly one a month.
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Bank Valuation Worksheet
A discounted cash flow does not work on a lender, so this uses the one identity that does: the justified multiple of tangible book, derived from what the equity earns against what it costs. Runs forwards to a fair value and backwards to the return the market price already assumes.
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Withdrawal Order Sequencer
Projects four retirement drawdown orders year by year across taxable, tax-deferred and Roth accounts, with every intermediate column visible: the gross-up for tax, the dividend drag, the cost basis amortizing as you sell. Same money either way; the spread is a year of spending.
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Concentration Risk Worksheet
Prices what a large position in one company costs you, in dollars, against the identical portfolio diversified. Also settles whether holding vested employer stock is a decision at all, which it is, and what the tax of unwinding it actually comes to.
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Social Security Claiming Calculator
Computes the benefit at every claiming age from the statutory reduction and credit rules, then runs the break-even against a real discount rate you choose. Contains no dollar amounts of its own: you bring your primary insurance amount from ssa.gov.
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Rent vs Buy Calculator
Finds your break-even year month by month, including the round trip transaction cost most people never count. Unlike almost every other calculator, it invests the surplus on both sides rather than only the renter's, which is the assumption that decides the answer.
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Reverse DCF Calculator
A forward DCF mostly hands your own growth assumption back to you. This takes the price as given and solves for the growth it requires, with a thirty-step bisection laid out on the sheet so you can watch it converge. No macros.
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Normalized Earnings Worksheet
A price to earnings ratio has two parts and only one of them is a fact. Enter ten years of margins, strip the items that were real only once, and see the multiple you are actually paying next to the one the screen shows.
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Investment Fee Drag Calculator
What are your fees actually costing you, in dollars and in years of extra saving? List your holdings, add the advisory layer, and a month-by-month engine prices the whole arrangement. The ladder shows what switching would be worth before you switch.
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DCF Valuation Model
A ten-year discounted cash flow model for valuing a single company, with an explicit WACC build and a sensitivity grid across discount rate and terminal growth. It also runs backwards: the reverse DCF solves for the growth rate today's share price already assumes, which is usually the more useful number.
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Order of Operations Allocator
Where does the next dollar go? Enter your income, expenses, debts, and account room, and a nine-step waterfall draws what each step needs before passing the rest down. The contribution limits are left blank on purpose, because a limit typed into a spreadsheet goes stale without telling you.
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Savings Rate & FIRE Tracker
Twelve rows a year is the whole habit. Log income, spending, and dollars invested, and the dashboard returns your savings rate, your progress to the target, your coast number, and how far off financial independence is at your current pace. Includes the savings rate table that shows why a 50% rate takes about 17 years and a 10% rate takes about 51.
Details and download →