Enter a starting amount, rate, term, and compounding frequency, with an optional monthly contribution, to see the maturity value and interest earned.
Cumulative contributions vs. projected value, year by year.
| Year | Contributed (cumulative) | Value | Growth |
|---|
Compound growth adds earned interest back into the principal each period, so future interest is calculated on a larger base — that's what "compounding frequency" controls: maturity = P × (1 + r/n)^(n×t). More frequent compounding produces a slightly higher return at the same stated rate.
It lets you model a lump sum that also receives regular top-ups — a hybrid between a one-time deposit and a pure SIP. If you're only ever adding money monthly with no starting lump sum, the dedicated SIP Calculator is a more natural fit.
The difference shrinks the more frequent compounding already is — daily vs. monthly matters far less than monthly vs. annual, at the same stated rate. On $100,000 at 8% over 10 years, annual compounding yields about $215,900, while daily compounding yields about $222,500 — a modest but real difference.
No — this is a projection based on a constant assumed rate you enter. Real investments and bank rates fluctuate, and past performance doesn't guarantee future results.
Divide 72 by your annual return and you get, near enough, the number of years for money to double. At 8% that's 9 years — the exact figure is 9.01, so the shortcut is genuinely accurate rather than merely convenient. It's a useful sanity check on any projection: if a calculator tells you money doubles in five years at 8%, the calculator is wrong.
The approximation drifts at extremes. Above roughly 20% it starts to understate the time required, and it says nothing at all about volatility — a portfolio averaging 8% with wild swings does not behave like a savings account paying a steady 8%, even though both produce the same number here.
The single largest error in compound-interest projections isn't the rate — it's forgetting inflation. A projection in nominal terms tells you how many dollars you'll hold, not what those dollars will buy.
$100,000 growing at 8% for 30 years reaches $1,006,265.69. If inflation runs at 3% over the same period, the honest figure is the one you get from a 5% real return: $432,194.24 in today's purchasing power. Both numbers are correct; they answer different questions. The second is the one that tells you whether you can retire.
The practical fix is to enter a real rate — your expected return minus expected inflation — whenever the projection runs more than about a decade. The result is less impressive and considerably more useful.
Over short horizons most of your balance is money you deposited. Over long ones, most of it isn't. That crossover is the entire argument for starting early, and it's worth seeing rather than being told: run the same monthly contribution over 10 years and over 30, and compare how much of each final balance is contributions versus growth.
This is also why a few years of delay costs more than it seems. The years you lose are the last ones — the most productive years in the sequence, when the balance is largest — not the first ones, when it's small.
Also want SIP or CAGR projections? Use the combined Investment Calculator. To see how much of the growth is compounding rather than the deposits themselves, compare against the Simple Interest Calculator. To solve for rate, term or payment instead of balance, use the Finance Calculator. The same ground is covered chapter by chapter in our book, From Paycheck to Portfolio. Compound growth is a geometric sequence — the Number Sequence Calculator shows the same maths in its general form. Compounding forward and discounting backward are the same equation from opposite ends; the present value calculator handles the backward direction.