Compound Interest Calculator

Enter an amount, a rate, and a number of years. See what it grows to and how much of that you never had to earn.

Starting amount

Annual return

Years

years

Start date

How to use

Enter your starting amount, the annual return, and how many years the money stays invested. Move the start date if the money goes in later than today.
Read the ending value and the split between what you put in and what it earned.
Open Deposits to add money as you go. A recurring amount goes in every month or once a year, starting in a month you choose, and can stop after a set number instead of running the whole term. A one-time lump sum lands in a single month.
Open Settings to change how often interest is credited, or to adjust the inflation rate behind the today's-dollars figure.
Switch between Chart and Schedule to watch the curve or read it year by year. Click any year to open its months.
Export the schedule to CSV if you want to keep it.

$10,000 at 7%, left completely alone:

The last decade adds more than the first two combined. That is the whole shape of compounding: it is slow, and then it is not.

Two people both retire at 65, both earning 7%:

The first person puts in $48,000 less and finishes $37,000 ahead. The ten extra years did more work than doubling the deposit.

• $500 a month for 30 years at 7% reaches $609,986 from $180,000 deposited. Two thirds of the ending balance is growth.
• That same $609,986 is worth about $251,000 in today's money once 3% inflation is taken out. Both numbers are true and the second is the one you spend.
• A steady return is an assumption. Real markets deliver the average as a series of good and bad years, so run a pessimistic rate too and see whether the plan still holds.