The Compound Interest Formula
Compound interest is interest calculated on both your original principal and the interest that has already accumulated — which is why Albert Einstein reportedly called it one of the most powerful forces in finance. The formula is:
A = P × (1 + r/n)^(n×t)
Where A is the final amount, P is your principal, r is the annual interest rate (as a decimal), n is the number of times interest compounds per year, and t is the number of years invested.
Why Compounding Frequency Matters
The more frequently interest compounds — daily versus annually, for example — the faster your money grows, because each compounding period adds interest on top of previously earned interest. The difference is small over a few years but becomes meaningful over a decade or more. Try switching the compounding frequency dropdown above to see how it changes your final amount.
Why Starting Early Matters More Than the Amount
Because compound growth is exponential, time in the market matters more than the size of your initial investment. $5,000 invested for 20 years at 10% annually grows to roughly $33,600 — but the same $5,000 invested for only 10 years only reaches about $13,000. Doubling your time roughly triples your growth at typical long-term rates, which is why starting to save or invest as early as possible — even with small amounts — pays off dramatically over a lifetime.
Real-World Use Cases
This calculator works for any compounding scenario: a fixed deposit at a Pakistani bank, a savings account, a recurring investment in mutual funds, or projecting retirement savings growth. Just enter your numbers and compounding frequency to see your realistic growth curve.