Compound Interest Calculator
See how an investment grows with compound interest over time.
This tool runs entirely in your browser. Your files are never uploaded to a server.
1647.01
Future value
647.01
Interest earned
What this calculator does
Projects the future value of a single lump-sum investment under compound interest, using a starting principal, annual interest rate, number of years, and how often interest compounds.
How to use it
Enter your principal, annual interest rate, and number of years, then choose a compounding frequency — annually, quarterly, monthly, or daily. Results update immediately as you change any value.
Worked example
With the defaults of a 1,000 principal, 5% annual rate, 10 years, and monthly compounding, future value = 1,647.01 and interest earned = 647.01 — the investment grows by about 65% over 10 years at 5% compounded monthly.
Formula
A = P × (1 + r/n)^(nt), where P is principal, r is the annual rate as a decimal, n is the number of compounding periods per year, and t is the number of years. Interest earned = A − P.
Why compounding frequency matters
More frequent compounding produces a slightly higher future value at the same nominal annual rate, because interest starts earning interest sooner. The difference between annual and daily compounding at typical rates is usually small — a percentage point or less over many years — but it's not zero, which is why the compounding frequency is part of a loan or investment's advertised terms.
Limitations
This models a single lump-sum deposit only — it doesn't add regular contributions, such as a monthly savings deposit, doesn't account for taxes, fees, or inflation, and assumes the interest rate stays constant for the entire period, which real-world rates rarely do.
Scope, sources and privacy
A = P(1 + r/n)^(nt) is the standard compound interest formula used in finance and taught in mathematics worldwide. Calculations run locally in your browser; the values you enter are never uploaded.
Frequently Asked Questions
- What does compounding frequency mean?
- It's how often interest is added to the principal — annually, quarterly, monthly or daily. More frequent compounding yields slightly more growth.
- Does this include regular contributions?
- No, this calculates growth from a single lump-sum principal only, without additional periodic deposits.
- What's the formula used?
- It uses A = P(1 + r/n)^(nt), the standard compound interest formula.