About

What 10-eok is, and who built it and why

10-eok answers a simple question with real historical data: "If you'd invested a fixed amount every month, how long would it have taken to reach $1M?"

What makes it different

• The question is reversed. Most calculators ask "how much will I have?" — 10-eok asks "how long until I hit my goal ($1M)?"
• Real daily prices. No assumed fixed return — every result is computed from actual historical daily closing prices.
• Transparent assumptions. Dividends, buy day, and taxes are all explained plainly, not buried in fine print.

How to use it

Pick a ticker, a monthly amount, and a buy day — that's it. You'll see how long it took to reach $1M and a chart of how your balance grew along the way. Change the amount or date and it recalculates instantly.

Who built this

10-eok is a personal project by 이정철 (Jeongcheol Lee), a developer and individual investor. It's not run by a financial firm or advisory service — I built it because I was genuinely curious "what if I'd started investing back then?" and wanted to check with real data instead of guessing. The focus is on being upfront about assumptions and limitations rather than making the numbers look better than they are. I'm not a licensed financial professional, and this site doesn't recommend any specific product.

The calculation logic is written as pure, tested functions with unit and golden tests. Prices come from Yahoo Finance, and economic data from the Federal Reserve Bank of St. Louis (FRED), refreshed automatically every day. The exact assumptions and simplifications behind the calculation are documented transparently on the How it works & FAQ page.

What's next

Currently supported tickers include QLD, TQQQ, QQQ, SPY, VOO, SCHD, and VT, with more on the way — ticker comparisons, inflation-adjusted contributions, and reverse-calculating the monthly amount needed for a target timeline. Bug reports and requests for new tickers are always welcome.

10-eok is an educational, informational tool — not investment advice or a solicitation. Reach out via the contact page or jclee7503@gmail.com.