Our free Compound Interest Calculator shows you how consistent saving and investing can grow your money over time. Answer four quick questions below for an instant, easy-to-understand breakdown of your potential growth.
Your answers — tweak any number and update
This is an estimate for illustration only, assuming a fixed rate of return applied consistently over the period. Real investment returns vary and are not guaranteed. This is not financial advice.
Compound Interest Calculator FAQs
How is this calculated?
We assume your money compounds monthly — meaning interest is calculated and added to your balance every month, using the annual rate you enter divided across 12 months. Your monthly contribution is added on top each month.
Does this account for inflation?
No — this calculator shows growth in future, uninflated pounds. If you'd rather see results in today's spending power, try entering a lower "expected return" that already accounts for inflation (for example, if you expect 7% growth and roughly 2.5% inflation, you could enter around 4.5%).
What return should I use?
It depends what you're investing in. A diversified stock market portfolio has historically averaged around 5–7% a year over the long term, though this isn't guaranteed. Cash savings accounts typically offer lower, more predictable rates. When unsure, it's safer to use a more conservative estimate.
Is my information stored anywhere?
No. Every calculation happens entirely in your own browser — we don't see, collect, or store any of the numbers you enter. See our Privacy Policy for more detail.