Compound Interest Calculator
See how money grows when interest compounds over time. Enter a starting amount, rate, years, and compounding frequency to estimate future value.
Calculate compound growth
Enter principal, rate, and time to calculate.
How it works
What this result means
The future value shows what your principal grows to when interest compounds repeatedly. Unlike simple interest, compound interest earns returns on prior gains — so the longer you wait, the faster it grows.
Formula:
FV = P × (1 + r/n)^(n × t)
Where:
FV = future value
P = principal (starting amount)
r = annual interest rate as a decimal (e.g. 5% = 0.05)
n = compounding periods per year (12 = monthly, 1 = annually)
t = time in years
- Divide the annual rate by the number of compounding periods (r/n)
- Add 1 and raise to the power of total periods (n × t)
- Multiply by the principal
- Result is the future value — interest compounding monthly grows faster than annually
Example
$5,000 at 5% compounded monthly for 10 years: FV = 5,000 × (1 + 0.05/12)^120 ≈ $8,235.
Use this tool for
- Estimating long-term savings or investment growth
- Comparing yearly, monthly, or daily compounding
- Seeing how time affects returns on a lump sum
Common questions
- What is the difference between compound and simple interest? Simple interest is earned only on the initial principal. Compound interest is earned on principal plus previously earned interest, so growth accelerates over time.
- What does compounding frequency mean? It is how often interest is added to the balance (e.g. yearly, monthly). More frequent compounding (e.g. monthly) yields slightly higher growth for the same annual rate.
- Can I use this for debt? Yes. The same math applies to debt: interest compounds on the outstanding balance. Use it to see how quickly debt can grow if only minimum payments are made.