About SumCrafter

SumCrafter is a collection of free financial calculators with one rule: show the math. Every tool displays its exact formula and a worked example you can check by hand. No sign-up, no email wall.

Why We Show the Math

I built this because I was tired of calculators that hand you a number and refuse to explain it. You type in years of savings, it spits out "$1.2 million," and you're supposed to just trust it. No formula. No example. No way to sanity-check. Just a black box wrapped in ads.

That never sat right with me. A calculator you can't verify is a calculator you shouldn't trust with real money decisions. So each tool here lays everything bare: the formula in plain sight, each input explained like you're a smart friend rather than a finance textbook, and an example with real numbers.

How We Verify Formulas & 2026 Tax Data

Every formula is published on the page that uses it and tested against hand-worked reference cases before a tool ships. Tax figures come from primary sources only — IRS Revenue Procedure 2025-32 for federal brackets, the Social Security Administration for the wage base, and each state's tax agency for state rules. The full source list and update process live on the methodology page, and how our calculators work walks through each tool's math.

I started with FIRE and debt payoff, the two areas where a good calculator genuinely changes what people do with their money. New tools go up most weeks. And if a result ever looks wrong to you, I want to hear about it. That's the whole point of showing the work.

Independent & Private by Design

SumCrafter is a one-person, independent project. Nothing here is financial advice. It's arithmetic, explained.

Start with the Coast FIRE calculator or browse all calculators — or tell me what to build next.