Compound Interest Calculator

Real compound interest: inflation, taxes and contributions included.

Most compound interest calculators show you a big, comforting number. This one shows you what that number will actually buy.

Enter your starting amount, how much you add and how often, and your expected return. The app projects your money month by month, then subtracts inflation and tax so you see the result in today's money — not tomorrow's.

WHAT MAKES IT DIFFERENT

• Inflation-adjusted results. A projected 500,000 in 25 years is not 500,000 of purchasing power. Both figures are shown side by side, always.
• Tax on gains. Choose tax paid every year or once when you cash out. Over a long horizon the gap between them is larger than most people expect.
• A real rate of return. The headline percentage is a proper money-weighted return, calculated from your actual contribution schedule — not a shortcut that pretends every deposit was made on day one.
• Best case and worst case. Turn on the rate range to project pessimistic, expected and optimistic scenarios at once.
• A methodology page that shows every formula, in the order it is applied, with a fully worked example. You can check every figure by hand.

WHAT YOU CAN SET

• Initial deposit and investment period, up to 100 years
• Regular contributions: daily, weekly, monthly, quarterly, semi-annual or annual
• Compounding frequency: daily, monthly, quarterly, semi-annual or annual
• Expected annual return, with an optional minimum and maximum
• Inflation rate
• Tax rate, charged annually or on exit

WHAT YOU GET

• A clear headline figure: what your money is worth in today's purchasing power
• Four summary tiles: total contributions, nominal value, value after tax, and value after tax and inflation
• A growth chart comparing all four lines across the whole period
• A breakdown of where the final amount comes from: your money, growth, and tax
• A full projection table, year by year or month by month, that expands to full screen

BUILT TO STAY OUT OF YOUR WAY

• Completely free. No subscriptions, no in-app purchases.
• Works fully offline. There is no server; every calculation runs on your device.
• No account, no sign-up, no email.
• No data collected. Your inputs are saved on your phone and never leave it.
• 43 languages, with number formatting that follows each one.
• Light and dark themes.
• Built for phones and tablets, in both portrait and landscape.

IMPORTANT

This app is an educational and planning tool. It projects mathematical outcomes from the assumptions you enter — it does not predict markets and it is not financial, investment or tax advice. Real returns vary, past performance does not guarantee future results, and tax rules differ by country. Consult a qualified adviser before making financial decisions.