Two people can save the exact same amount and end up with very different balances, purely because of when they started.
Free finance tool
Compound Interest Calculator
See how a lump sum plus monthly contributions grow over time. Calculated in your browser.
Assumption: monthly contributions are added at the end of each month; interest compounds at the frequency you select above.
| Year | Contributed | Interest earned | Balance |
|---|
How compound interest is calculated
Future value = principal × (1 + rate ÷ n)n × years, plus the future value of your monthly contributions growing at the same rate — where n is how many times per year interest compounds. Example: €1,000 at 6% compounded monthly for 10 years, with no extra contributions, grows to about €1,819. "Reach a goal" mode runs the identical formula backward, solving for the monthly contribution that gets a starting amount to a target by a chosen year instead of solving for the final balance.
Compound interest FAQ
What is compound interest?
Compound interest is interest calculated on both your original balance and the interest it has already earned, so growth accelerates over time instead of staying flat like simple interest.
How does compounding frequency affect returns?
The more often interest is added to your balance — daily vs. monthly vs. annually — the sooner that interest starts earning its own interest, which slightly increases your final balance at the same nominal rate.
Does this calculator include my monthly contributions?
Yes. Enter a monthly contribution amount and the calculator adds it to your running balance each month, alongside compounding on your existing balance.
What is the formula for compound interest with monthly deposits?
Future value = principal × (1 + rate ÷ n)^(n × years), plus the future value of your monthly deposits growing at the same rate — where n is how many times per year interest compounds.
Why does this calculator show an inflation-adjusted value?
A future balance buys less than the same amount today because prices rise over time. Enter an expected inflation rate to see your result in today’s purchasing power, not just the nominal total.
How does "Reach a goal" mode work?
Switch to Reach a goal, enter a target amount and a starting amount, and the calculator solves the same compound interest formula backward to tell you the monthly contribution needed to hit that target by your chosen year. It is the same maths as Grow my savings, just rearranged to solve for a different unknown.
Is this compound interest calculator free and private?
Yes. It runs entirely in your browser — no amounts are uploaded, stored or shared, and there is no sign-up.
Free compound interest calculator by ANUPRESS
Why the starting point matters more than the monthly amount
That’s the whole idea behind compound interest: your interest starts earning its own interest, and the earlier that begins, the more it compounds before you need the money. Someone who saves for ten years and then stops usually ends up ahead of someone who saves twice as long but starts a decade later contributing the same monthly amount, purely because the first person’s early contributions had more years to compound. It’s a strange result until you run the numbers yourself, which is the point of putting a real calculator in front of it instead of just describing it.
Does compounding frequency actually matter
Daily compounding beats annual compounding at the same nominal rate, but not by much. Over ten years, the difference between monthly and annual compounding on a typical savings rate is usually a few percent of the total, not a doubling. It’s real, and worth choosing correctly if your account states its compounding frequency, but it won’t rescue a low interest rate or make up for stopping contributions early.
Why there’s an inflation field
A balance that grows to €30,000 in fifteen years sounds better than it is if prices have also gone up over that time. The inflation field converts your result into today’s purchasing power, so you can see what that future balance is actually worth in terms of what it buys right now, not just the number on the screen. Leave it at 0% if you’d rather see the plain nominal total.
A quick word on the “vs simple interest” question
Simple interest is calculated only on your original balance, every time, so it grows in a straight line. Compound interest recalculates based on your current balance, including everything you’ve already earned, so it grows on a curve that gets steeper the longer it runs. Most savings accounts, and pretty much anything described as an “annual percentage yield,” use compound interest.
This tool shows the maths only. It isn’t investment advice, and a fixed rate of return isn’t guaranteed in real markets.