All tools

Twenty free pages: live delayed-quote lookups and the calculators that do not need a data feed at all. Nothing here asks for an account, an email or a download.

Market data (delayed, served through this site)

• US stock & ETF quote lookupLast price, day range, bid/ask, volume and 30-day implied volatility for any US-listed symbol.
• Stock watchlistA list of symbols saved in your own browser, refreshed on one click.
• Options implied moveTurns a symbol's IV30 into a plus/minus price range over the horizon you pick.
• Bid-ask spread costWhat crossing the spread actually costs, per share and per 100 shares.
• Market hours countdownWhether the US market is open right now, and how long until it changes.

Growing a balance

• Compound interestYear-by-year table of contributions versus growth.
• Dollar-cost averagingFixed monthly investing against putting the same money in on day one.
• Rule of 72How fast a rate doubles your money, and the rate needed to double by a date.
• Dividend reinvestmentReinvesting quarterly payouts versus taking them as cash.
• Expense ratio impactWhat a fund fee costs over decades, including the compounding it eats.
• ETF vs mutual fundStructural differences in trading, pricing and fees, plus a cost comparison.

Income and drawing down

• Dividend yieldTrailing yield, yield on cost and shares needed for a payout.
• Dividend incomePortfolio size and share count required for a target monthly income.
• Withdrawal rateHow many years a portfolio lasts at an inflation-indexed withdrawal.
• Emergency fundTarget, gap, months to fund, and the opportunity cost of holding it.

Everyday maths

• Percentage changeForward and reverse percentages, including the negative-base trap.
• Real returnReturn after inflation, in today's dollars.
• APY vs APRConvert between the advertised rate and the rate you actually earn.
• Mortgage paymentPrincipal and interest, total interest, and what an extra payment saves.
• Stock splitForward and reverse splits: new price, new share count, unchanged value.

How this site is built

Every page is a single file of plain HTML and JavaScript that runs in your browser. No framework, no remote scripts of mine, no tracking of what you type. The quote pages fetch one small JSON file from this same domain, about half a kilobyte, and the delayed feed is CBOE's public one. Calculators never send anything anywhere.

Not investment advice

These are arithmetic tools over numbers you enter. They do not recommend any security, do not model bad years, and cannot know your tax situation. Nothing here is investment, tax or legal advice.