Compound Interest Calculator
See what savings grow to over time, year by year, with inflation shown alongside.
The Number Most Calculators Leave Out
Compound interest calculators are good at producing a large and encouraging figure. Thirty years of saving turns into something that looks like wealth. What that figure does not tell you is what it will buy, because thirty years of inflation has been working in the other direction the whole time.
This one shows both. The headline balance is there, and beside it the same balance discounted back to today's money — which is the only one of the two you can compare to a price you know. It also breaks out what you put in against what the interest earned, because seeing the crossover year is more persuasive than any total.
Key features
- Regular contributions — a monthly amount alongside the starting balance, which is how most people actually save.
- Any compounding frequency — daily, weekly, monthly, quarterly or yearly, converted correctly to a monthly step.
- Inflation-adjusted total — what the final balance is worth in today's money.
- Year-by-year table and chart — with contributions and interest separated so the crossover is visible.
- CSV export — the whole schedule, for a spreadsheet.
This tool runs entirely inside your browser using native Web APIs. Your files and text are never uploaded to a server, never logged and never shared with third parties.
How to use: Compound Interest Calculator
- Enter what you have and what you add
A starting balance and a monthly contribution; either can be zero. - Set the rate and the years
Use a nominal annual rate. Long-term stock market averages are often quoted around 7% after inflation. - Choose the compounding
Monthly is the common default for savings accounts. - Read both totals
The headline balance, and what it is worth in today's money.
Technical specifications
| Processing location | Entirely in your browser — no server round trip |
|---|---|
| Data uploaded | None. Files and text never leave your device |
| Price | Free — no account, no trial, no usage cap |
| Category | Calculators |
| Works offline | Yes, once the page has loaded |
| Browser support | Chrome 90+, Edge 90+, Firefox 90+, Safari 15+ |
| Interface languages | English, 中文, हिन्दी, Español, العربية |
Frequently asked questions
Why is the inflation-adjusted figure so much lower?
Because inflation compounds too. At 2.5% a year, prices roughly double in 28 years, so a pound in thirty years buys about what 48 pence buys now. That is not pessimism, it is the same arithmetic running in the other direction — and it is why a 7% return with 2.5% inflation is really about 4.4% of actual growth.
When are the contributions added?
At the end of each month, which is the conservative reading. Money paid in at the start of a month earns interest for that month, so a real account paying you on the first will do very slightly better than this shows. Over thirty years the difference is real but small.
Does compounding daily instead of yearly make much difference?
Less than people expect. At 7%, yearly compounding gives 7% and daily gives about 7.25% — worth having, not worth choosing a worse account for. The contribution amount and the number of years both matter enormously more.
Does this account for tax?
No, and deliberately. Tax on savings and investments depends on your country, your allowances, the account type and your income, and a single number pretending to cover that would be wrong for almost everyone. Treat the result as gross and apply your own situation to it.
What rate should I use?
For a savings account, the rate you are actually offered. For investments, there is no right answer — long-run global equity returns have averaged somewhere around 5% above inflation, but any particular thirty years can be well above or below that. Try two or three rates and look at the spread rather than trusting one.