Compound Interest Calculator
See how a lump sum grows over time when interest compounds. Set your starting amount, rate, number of years and how often interest is added to watch your balance build.
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Uses the standard compound interest formula A = P(1 + r/n)^(nt). This assumes a fixed rate and no further deposits or withdrawals.
Frequently asked questions
What is the compound interest formula?
The future value is A = P(1 + r/n) raised to the power of n times t, where P is the starting amount, r is the annual rate as a decimal, n is how many times interest compounds per year, and t is the number of years.
Why does compounding frequency matter?
The more often interest is added, the more often you earn interest on interest. Monthly compounding grows a balance slightly faster than annual compounding at the same headline rate, though the difference is usually modest.
Does this account for regular deposits?
No. This calculator models a single lump sum left to grow. If you plan to add money regularly, your final balance will be higher than the figure shown here.