Compound Interest Calculator UK
Calculate how your savings or investments could grow over time with compound interest and regular monthly contributions. See your projected future value, total contributions and interest earned.
Calculator
What this means
Compound interest means you earn returns not just on your original money but also on the interest already added. Over long periods this snowball effect can make a big difference, especially when you add regular contributions.
How to use this calculator
- Enter your starting amount and any regular contributions.
- Enter the growth rate and number of years.
- See how your money could grow with compounding.
Worked example
£5,000 invested at 5% for 20 years, no further contributions.
- Returns are reinvested and earn returns themselves.
- £5,000 × (1.05) to the power of 20 ≈ £13,266.
After 20 years it could grow to about £13,266 before fees and inflation.
Who this is for
- Long-term savers and investors.
- Anyone planning for a goal years away.
- People wanting to see the power of starting early.
Why compounding is so powerful
Compounding means your returns generate further returns, so growth accelerates the longer you stay invested. Starting earlier matters more than the amount, because time does the heavy lifting.
Real investment returns aren't guaranteed and fees and inflation reduce them. Treat projections as illustrations, not promises, and diversify rather than relying on a single outcome.
Frequently asked questions
Compound interest is interest earned on both your original deposit and the interest already added. The more often interest compounds and the longer you save, the faster your balance grows.
Simple interest is paid only on your original amount. Compound interest is paid on the growing balance, so it accelerates over time — which is why starting early matters so much.
Use the AER on a savings account, or a realistic long-term estimate for investments (often 4–7% before charges and inflation). Investment returns are not guaranteed and can fall as well as rise.
Divide 72 by your annual growth rate to estimate the years it takes money to double. At 6%, that's about 12 years — a quick mental check on compounding.
No. The projection shows nominal growth. To gauge real spending power, subtract an inflation estimate from your assumed return.
Disclaimer
This calculator provides estimates for guidance only. It is not financial, legal or tax advice. Always check official sources or speak to a qualified professional before making decisions.
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