See your money compound.
The compound interest & dividend calculator that shows the whole picture
Add contributions, reinvest dividends (DRIP), solve for a goal and adjust for inflation — with a clear chart and year-by-year breakdown. Free, no sign-up.
Compound interest calculator
Adjust the inputs — results update instantly.
Future value
£144,573
Total contributions
£58,000
Investment growth
£86,573
Balance over time
Stacked: your contributions vs. compounded growth.
Year-by-year breakdown
| Year | Balance | Contributions | Growth |
|---|---|---|---|
| 1 | £13,201 | £12,400 | £801.42 |
| 2 | £16,634 | £14,800 | £1,834 |
| 3 | £20,315 | £17,200 | £3,115 |
| 4 | £24,262 | £19,600 | £4,662 |
| 5 | £28,495 | £22,000 | £6,495 |
| 6 | £33,033 | £24,400 | £8,633 |
| 7 | £37,900 | £26,800 | £11,100 |
| 8 | £43,118 | £29,200 | £13,918 |
| 9 | £48,714 | £31,600 | £17,114 |
| 10 | £54,714 | £34,000 | £20,714 |
| 11 | £61,147 | £36,400 | £24,747 |
| 12 | £68,046 | £38,800 | £29,246 |
| 13 | £75,444 | £41,200 | £34,244 |
| 14 | £83,376 | £43,600 | £39,776 |
| 15 | £91,882 | £46,000 | £45,882 |
| 16 | £101,003 | £48,400 | £52,603 |
| 17 | £110,783 | £50,800 | £59,983 |
| 18 | £121,270 | £53,200 | £68,070 |
| 19 | £132,515 | £55,600 | £76,915 |
| 20 | £144,573 | £58,000 | £86,573 |
How compounding works
Compounding is growth on growth. Each period, your returns are added to your balance — and the next period earns returns on that larger balance too. Over long horizons this snowball effect dwarfs your original contributions.
A lump sum grows by FV = PV × (1 + r)ⁿ, where r is the periodic rate and n the number of periods. Monthly compounding splits the annual rate into twelve.
Regular deposits form an annuity:FV = PMT × [(1 + r)ⁿ − 1] / r. We add contributions at the end of each period (ordinary annuity).
With DRIP, dividends buy more shares, which pay more dividends. Add dividend growth and your yield on cost rises year after year — the engine behind real passive income.
Why time matters more than rate
Invest £10,000 at 7% with no further deposits and you have roughly £19,672 after 10 years, but about £76,123 after 30 years. The extra two decades did far more than the first one — because each year compounds on an ever-larger base. Starting earlier usually beats trying to earn a higher return.
Pick the right calculator
One engine, four lenses. Each mode tailors the inputs and outputs for a specific question — all using the same correct compounding math.
Ready to put compounding to work?
A projection only matters once you start investing. These are starting points to research a broker or ETF platform that suits you. We are not recommending a specific product — compare fees, eligibility and protections before you commit.
Affiliate disclosure: some links may be sponsored and we may earn a commission at no cost to you. This is not financial advice.
Frequently asked questions
How does this compound interest calculator work?
Enter a starting amount, a regular contribution, your expected annual return and a time horizon. Compoundly applies your chosen compounding frequency (monthly or annual), adds contributions at the end of each period (ordinary annuity), and shows the future value, the split between what you put in versus growth, a chart, and a year-by-year table.
What is DRIP and how is it calculated?
DRIP stands for Dividend Reinvestment Plan. Instead of taking dividends as cash, they buy more shares, which then pay more dividends. In the DRIP mode you enter a dividend yield and an annual dividend growth rate; reinvested dividends are added back to your balance each period, and we also show projected annual passive income at the end (yield × ending balance).
What does the goal-seek calculator do?
Goal-seek inverts the maths. You give it a target future value, an expected return and a number of years, and it solves for the monthly contribution required to get there using the closed-form annuity formula. It then runs the forward projection with that contribution to confirm the answer.
Does it account for inflation and taxes?
You can add an optional inflation rate to see the real (purchasing-power) value alongside the nominal figure. Taxes and platform fees are not modelled by default — reduce your expected return to approximate fee drag, and remember that results are estimates, not advice.
What compounding assumption do you use?
Contributions are added at the end of each compounding period — the ordinary annuity convention used by most calculators. With monthly compounding selected, the annual return is divided by twelve and applied each month. This is stated on the tool and documented in our method notes.
Is Compoundly free and is this financial advice?
Compoundly is completely free to use and requires no sign-up. It is an educational projection tool, not financial advice. Investment returns are never guaranteed and you can lose money. Always do your own research or consult a regulated adviser.