Compound Interest: Calculator

See exactly what time and steady deposits do to your money. Enter a starting amount, a rate, a monthly deposit and the years you are willing to wait — the future value and a full growth chart redraw the instant you change any assumption. Most calculators stop at one number. This one runs an exact month-by-month simulation in decimal arithmetic: interest credited annually, semi-annually, quarterly or monthly; deposits at the start or end of the month; nominal rate and effective annual rate (APY) stated separately instead of quietly conflated; even negative rates handled without breaking. Then it lets you save each projection as a named scenario and lay two of them over each other on one chart. WHAT YOU GET • Your future balance in three honest numbers — final value, what you put in, and the interest time added — recalculated the instant you move a slider • A growth chart that separates your own deposits from compound growth, so you can spot the year interest starts outworking your paycheck • The real answer to "does monthly compounding matter?" — nominal rate and effective APY shown side by side on every projection • An "in today's money" toggle that restates your 30-year balance using your own inflation assumption — never a forecast we invented for you • Saved scenarios with names and colours — house deposit at 4.5%, index fund at 7% — each reopening exactly as you left it • Side-by-side comparison: two growth curves overlaid on one chart, with final balance, deposits and interest lined up underneath PERFECT FOR • Savers deciding whether the high-yield account or the index fund wins over the next 15 years • Parents starting a college fund who want to see what 150 a month actually becomes by graduation • Anyone negotiating with their future self — one more year of deposits, one chart to prove what it buys • Students learning why a 7% nominal rate is not a 7% effective rate, with numbers they chose themselves WHY NOT JUST A SPREADSHEET? A spreadsheet makes you build the formula yourself, and one wrong cell compounds the error — literally — over 600 monthly rows. This app simulates every month in exact decimal arithmetic, lands interest precisely on compounding boundaries, and reproduces the textbook formulas to the cent. You move a slider; it does the maths. PRIVATE BY DEFAULT Everything runs on your device. No account, no sign-up, and your numbers are never uploaded anywhere. Amounts display in your own currency and your keyboard's own decimal separator just works. FULL ACCESS Full Access unlocks unlimited saved scenarios and side-by-side scenario comparison. It is offered as an auto-renewing Weekly or Yearly subscription, or a one-time Lifetime purchase. Prices are shown in the app before you commit; subscriptions renew unless cancelled at least 24 hours before the current period ends and can be managed in your App Store account settings. Download Compound Interest Calculator and find out what your monthly deposit is really worth ten years from now. Terms of Use: https://leanstudio.asia/terms-of-use Privacy Policy: https://leanstudio.asia/privacy-policy Support: support@leanstudio.asia