Add the numbers for your scenario.
01Finance & Loans toolCalculated result
Compound Interest
Grow savings with regular contributions over time.
100% FreeRuns instantlyNo watermark
- 1Enter detailsAdd the numbers for your scenario.
- 2CalculateVootkit updates the result instantly.
- 3ReviewCheck totals, notes and breakdowns.
Private by designProcessed on your device where possible.
Works on any deviceDesktop, tablet and mobile browsers.
No installationOpen the page and start working.
Always free coreUse the free plan for everyday tasks.
How to use Compound Interest
Vootkit updates the result instantly.
02Check totals, notes and breakdowns.
03Copy the answer into your workflow.
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Your work is processed locally in your browser where possible and is never added to a Vootkit upload library.
Learn more about privacyCompounding is famously powerful and famously hard to feel. The gap between what people expect and what the arithmetic produces is largest at exactly the horizons that matter — twenty years and beyond.
What Compound Interest does
Projects what a starting balance plus regular monthly contributions becomes over time at a given annual return.
It separates what you put in from what the growth added, which is the comparison worth seeing. Over long periods the growth typically overtakes the contributions, and the year it does is the point of the whole exercise.
Inputs and useful reference points
| Compounding | Monthly, matching the monthly contribution |
|---|---|
| Return range accepted | −50% to 100% a year — negative returns are allowed deliberately |
| Time horizon | 1–70 years |
| Rule of 72 | Years to double ≈ 72 ÷ return, so 7% doubles in about 10 years |
| Long-run stock market average | Often cited around 7% after inflation — an average, not a promise |
| What is not modelled | Fees, tax, and inflation |
| Currencies | USD, EUR, GBP, CAD, AUD, INR |
Detailed steps
- Enter your starting amount and monthly contribution.
- Choose a return. Try a pessimistic figure as well as an optimistic one — the spread between them is the honest answer.
- Set the number of years.
- Compare total contributed against growth to see when compounding starts doing the work.
Worth knowing
Run it once with your expected return and once with two percentage points less. Fees, tax and a bad decade all come out of the same figure, and a plan that only survives the optimistic number is not a plan. The gap between the two runs is the risk you are carrying.
Frequently Asked Questions
What return should I use?
That is the one input nobody can give you honestly. Long-run stock market averages are often quoted around 7% after inflation, but any individual decade can be far above or far below that. Model a range rather than a single figure.
Does this account for inflation?
No. The result is in today’s currency units, not today’s purchasing power. To think in real terms, subtract expected inflation from your return — a 7% return with 3% inflation is roughly 4% real.
Are fees and tax included?
Neither. A 1% annual fee is a straight deduction from your return and compounds against you exactly as growth compounds for you, which is why it costs far more over thirty years than it looks like it should.
Why does the growth accelerate so sharply?
Because returns are earned on previous returns, not just on what you put in. Early years look disappointing and late years look implausible — that shape is the whole point, and it is why time in the market is the variable people underestimate.
Is Compound Interest free?
Yes. The Vootkit free plan includes 5 tool runs a day. Upgrade to Vootkit Pro for unlimited daily use, an ad-free workspace and saved workflows.
Are my files uploaded?
No. Compound Interest runs entirely in your browser — your file is processed on your own device and never sent to a server. There is nothing for us to store or delete.
Do I need to install anything?
No. Compound Interest works in any modern browser on desktop, tablet or phone. Open the page and start.
How often can I use it? Is there a daily limit?
On the free plan you get 5 tool runs a day. When you reach the limit you'll see a prompt to upgrade, and it resets the next day. Vootkit Pro removes the cap entirely for unlimited daily use.
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