Compound Interest Calculator
Project how your savings grow over time with compound interest and optional regular deposits. See your final balance, total contributions and total interest earned, plus a year-by-year breakdown. Everything runs in your browser — your figures are never sent anywhere and nothing is stored.
Year-by-year breakdown
| Year | Balance | Interest that year |
|---|
How to use the compound interest calculator
- Enter your initial principal, the annual interest rate and the number of years.
- Choose how often interest compounds — annually, semi-annually, quarterly, monthly or daily.
- Optionally add a regular contribution and set whether you deposit it monthly or yearly.
- The results and the year-by-year table update instantly as you type.
The calculator uses the standard compound interest formula with the future value of a series of end-of-period contributions. A rate of 0% still works — the balance simply equals your principal plus all deposits made, with no growth.
More PAYATE tools
Frequently asked questions
What is compound interest?
Compound interest is interest calculated on both your original principal and the interest already added to it. Because each period's interest earns interest in later periods, your balance grows faster over time than it would with simple interest — an effect often called compounding.
What does compounding frequency change?
The compounding frequency is how often interest is added to the balance — annually, semi-annually, quarterly, monthly or daily. More frequent compounding means interest starts earning interest sooner, so a higher frequency gives a slightly larger final balance for the same annual rate.
How are regular contributions handled?
Optional regular contributions (monthly or yearly) are added at the end of each period and then compound alongside your principal. This is the future value of a series: the calculator sums the growth of every deposit through to the final year.
What is APR versus the rate I enter?
You enter a nominal annual rate. The calculator splits it across the compounding periods. The effective annual yield can be a little higher than the nominal rate because of compounding — that difference is what more frequent compounding captures.
Does a 0% rate still work?
Yes. With a rate of 0% no interest is earned, so the final balance is simply your initial principal plus all the contributions you made. The calculator handles this as straightforward accumulation with no growth.
Is my data sent anywhere?
No. Every calculation runs entirely in your browser — your figures are never uploaded to a server and nothing is stored. You can use it freely for private savings planning.