# Compound interest calculator

See how a starting amount and regular monthly additions grow with compound interest. Pick how often interest compounds and get a year-by-year breakdown.

Interactive calculator (runs in the browser): https://www.trackmysubscriptions.com/tools/compound-interest-calculator

## The formula

For a single amount, A = P x (1 + r/n)^(n x t): principal P, yearly rate r, n compounding periods a year, t years. Monthly additions are added at the end of each month and earn the equivalent monthly rate from then on.

## Does compounding frequency matter?

Less than most people think. $10,000 at 6% for 10 years becomes $17,908.48 compounded yearly and $18,220.29 compounded daily, a difference of $311.81. The rate and the time matter far more than the frequency.

## Worked example with monthly additions

Start with $5,000, add $100 a month, earn 7% compounded monthly. After 15 years you have put in $23,000 and the balance is $45,940.96. $100 a month is roughly what two or three streaming services cost; see [what yours would be worth invested](https://www.trackmysubscriptions.com/tools/subscription-investment-calculator).

## FAQ

### What is compound interest?

Interest that is added to the balance and then earns interest itself, so growth speeds up over time.

### Is daily compounding much better than monthly?

Only slightly. On $10,000 at 6% over 10 years, daily compounding beats yearly by $311.81.

### When are monthly additions added?

At the end of each month. They earn interest from the following month.