Money & crypto · no black boxes

Calculators that show their work.

Fast, free tools for real money and crypto decisions. Every formula and assumption is on the page, nothing you type ever leaves your browser, and there is no signup.

Why trust these: each calculator states its formula and what it excludes, so you can check the math instead of trusting a black box. Methods are reviewed by YJ Quant, a quantitative researcher — see About.

Money

Planning, debt, and investing decisions — with tax and inflation where they matter.

Compound interestGrowth of savings with regular contributions

Coast / Barista FIRE — when your savings can coast to retirement
Debt payoff: avalanche vs snowball — payoff date and total interest, side by side
Mortgage overpayment — what an extra monthly amount saves
Lump sum vs dollar-cost averaging — which wins, and when
After-tax, inflation-adjusted return — your real return, not the headline

Crypto

Risk and yield tools for leverage and DeFi — built to be precise about the parts most calculators gloss over.

Staking after tax — real yield once tax is taken out

How this site works

Each tool runs entirely in your browser and is built to answer one question well. Where a calculation involves choices — tax treatment, margin type, fees — the page says which choice it made and why, so the number is auditable. This is deliberately the opposite of a tool that hands you a figure and hopes you don’t ask how it got there.