Compound Interest Calculator
See how savings grow with compound interest.
Contributions are added at the end of each month and the balance is grown using a monthly rate equivalent to your chosen compounding frequency. Results are estimates and don't account for taxes, fees, or inflation. Amounts are shown in your own currency.
Use on any page (bookmarklet)
Want Compound Interest Calculator without leaving the page you're on? Drag the button below to your bookmarks bar, then click it on any website to open Compound Interest Calculator right there — it runs entirely in your browser.
Use responsibly: a bookmarklet runs on whatever page you click it on. Avoid sensitive sites such as online banking, payment, or healthcare pages — you run it at your own risk. Everything is processed locally and no data is sent anywhere. See our Terms.
- Show your bookmarks bar if it's hidden — Ctrl+Shift+B (⌘+Shift+B on Mac).
- Drag the button above onto the bookmarks bar.
- Open any website and click the bookmark — the Compound Interest Calculator panel appears in the top-right corner. Use ✛ to move it between corners, or ›/‹ to tuck it against the edge and pull it back out.
- Click the bookmark again (or the ✕) to close it.
Note: a few sites with strict security policies may block bookmarklets.
Examples
1,000 + 100/mo at 7% for 10 years
Input
Start 1000 · +100/mo · 7% · Monthly · 10 yr
Output
Future balance 19,318.14 · Put in 13,000 · Interest 6,318.14
5,000 lump sum at 5% for 20 years
Input
Start 5000 · no deposits · 5% · Monthly · 20 yr
Output
Future balance 13,563.20 · Put in 5,000 · Interest 8,563.20
About this tool
This free online compound interest calculator shows how savings and investments grow over time. Enter a starting amount, an optional monthly contribution, an annual interest rate, and a term, and it projects your future balance — splitting it into what you put in and the interest you earned. The growth chart and result update instantly in your browser with no upload.
How to use
- Enter your starting amount (principal).
- Add a monthly contribution, or leave it at 0 for a lump sum.
- Enter the annual interest rate and number of years.
- Pick how often interest compounds and read your projected balance.
Good to know
The earlier you start and the longer you stay invested, the larger the interest slice becomes relative to your contributions — that's compounding at work. This is a gross estimate before taxes, fees, and inflation, so use it to compare scenarios rather than as a promise of returns.
Frequently asked questions
What is compound interest?
Compound interest is interest earned on both your original money and the interest it has already earned. Because each period's gains start earning too, the balance grows faster over time — the snowball effect that makes long-term investing and saving powerful.
How does this calculator work?
It grows your starting amount month by month using a monthly rate equivalent to your chosen compounding frequency, adds your monthly contribution at the end of each month, and tracks the running balance. The chart shows year-by-year growth split into contributions and interest.
Is this compound interest calculator free?
Yes — it's a completely free online compound interest calculator with no sign-up. Everything runs in your browser.
What does compounding frequency change?
It's how often interest is added to the balance: annually, semi-annually, quarterly, monthly, or daily. More frequent compounding earns slightly more because interest starts earning interest sooner, though the difference is small at typical rates.
Can I include monthly deposits?
Yes. Enter a monthly contribution and the calculator adds it every month, then compounds the growing balance. Regular contributions usually matter far more than compounding frequency over the long run.
Does it account for tax or inflation?
No. The result is a gross estimate before taxes, fees, and inflation. Real returns will be lower once those are taken out, so treat the number as an illustration rather than a guarantee.
Is my data uploaded anywhere?
No. The calculation runs entirely in your browser with no upload, so your figures stay private.
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