Compound interest calculator
See what your money grows to when the interest starts earning interest. It's slow, and then it isn't. The interesting years are the ones most people never stay for.
Updated for the 2026/27 tax year · reviewed
Your savings
Compounding
Your savings would grow to
£47,527
after 10 years, monthly compounding
Total contributed
£34,000
Interest earned
£13,527
Share of pot from interest
28.5%
Balance over time
How much of the growing balance is money you put in, versus interest on top.
Compounding works. Life interrupts it.
A real plan has a mortgage, a pension and years where you save less. See this pot growing alongside all of them, instead of on its own in a straight line.
Create your free accountHow this calculator works
We grow your starting lump sum and monthly saving using the standard compound interest formula, adding interest at the frequency you choose - daily, monthly or annually. Each time interest is added, it starts earning interest itself, which is why the balance curves upward rather than climbing in a straight line.
The chart splits the growing balance into what you actually paid in (contributions) and what came from interest on top. Over long periods, especially at higher rates, interest can end up contributing more to the final total than your own contributions did.
This assumes a fixed interest rate and a steady monthly saving for the whole period - real savings rates move with the market, and few people save exactly the same amount every month. Treat the result as an illustration of how compounding works, not a guarantee.
Questions people ask
What is compound interest?
Interest paid on both your original money and the interest it has already earned. £10,000 plus £200 a month at 5% grows to about £47,500 in ten years - roughly £13,500 of that is interest earning interest.
How often is interest compounded in UK savings accounts?
Most UK easy-access accounts compound daily or monthly and quote an AER so accounts can be compared fairly. The difference between monthly and annual compounding at the same quoted rate is real but small - this calculator lets you switch and see it.
Is the interest rate guaranteed?
No - variable-rate accounts change with the market. Use today's rate as a starting point and try a lower rate to see a cautious scenario.
Last reviewed against 2026/27 UK rules. Projections are estimates for education, not financial advice. Understanding your projections.
A calculator answers one question at a time.
The planner keeps all of them next to each other, so an overpayment you model today still shows up in the pension picture in twenty years.
- Free to start
- No card needed
- Your figures carry over