TALLIVO
toolsabout
Your numbers will appear here as you use the tools.
home / compound interest calculator
Investing & growth

Compound Interest Calculator

Project how an investment grows over time with regular contributions — and watch the gap between what you put in and what compounding adds.

InputsCI
$
$
%
Future value30 yrs
$691,150
total contributed$190,000
interest earned$501,150
future value
$691,150
contributed
$190,000
growth
$501,150
Growth over time
Balance Contributed
$0$187k$373k$560k$746k2026203620462056

How compound growth is calculated

Each month your balance earns its share of the annual return, then your contribution is added. Because last month's growth also earns growth, the total accelerates — the essence of compounding.

FV = P(1 + r/12)^(12t) + PMT · [ ((1 + r/12)^(12t) − 1) / (r/12) ]

P is your starting amount, r the annual return, t the years, and PMT your recurring contribution. The chart shows total value against total contributed, so the widening gap is your compounded growth.

Common questions

What is compound interest?
Compound interest is interest earned on both your original money and the interest it has already earned. Over long periods this snowballs — which is why starting early matters so much.
How often does interest compound here?
Monthly. Your return rate is divided by 12 and applied each month, and contributions are added at the end of each period.
Does this account for taxes or inflation?
No — it shows nominal, pre-tax growth. For a rough real (inflation-adjusted) return, subtract about 2–3% from your rate.
What return rate should I use?
The S&P 500 has historically averaged roughly 10% nominal (about 7% after inflation) over the long run, but returns vary widely year to year. Use a rate you're comfortable with.

How we calculate this

Monthly compounding with end-of-period contributions (an ordinary annuity). Nominal, pre-tax figures — not financial advice.

Full methodology & sources →
Related calculators
InvestDividend / DRIP CalculatorHomeMortgage CalculatorMoneyPaycheck CalculatorMoneyIncome Tax Calculator

Projections are estimates based on a constant assumed return; real markets fluctuate and past performance does not guarantee future results. For general information only — not financial advice.