Compound Interest Calculator

Use our UK Compound Interest Calculator to estimate how your savings or investments could grow over time. Whether you're saving for a house, retirement, or a rainy day, this tool helps you visualise the power of regular contributions and compound growth. The power of compounding interest can be quite surprising.

How Compound Interest Works

Compound interest means you earn interest on both your initial investment and the interest you've already earned. Over time, this can lead to exponential growth, especially when you make regular monthly contributions. This calculator assumes monthly compounding, which is standard for most UK savings and investment accounts.

Frequently Asked Questions

Is this calculator accurate?

This tool provides a good estimate based on consistent monthly contributions and a fixed annual interest rate. It does not account for inflation, tax, or changes in interest rates over time.

What interest rate should I use?

If you're using a savings account, check your provider’s current rate (e.g. 4.5%). For investments, a long-term average of 5%–8% is often used, though returns are not guaranteed.

How often is interest compounded?

This calculator uses monthly compounding, which aligns with most UK savings accounts and investment platforms. This means interest is calculated and added each month.

Is there a limit to how much I can contribute?

There’s no technical limit in this tool. But in real life, ISA limits (£20,000/year in 2025) or pension contribution rules may apply depending on your savings method.

Next Steps

Want to explore other money tools? See our full range of financial calculators including a take-home pay calculator, mortgage calculator, and more.