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Compound Interest Calculator
See how your money grows over time with the power of compounding.
Compound Interest Formula
The exact formula used by banks and financial advisers
Growth Visualisation
Interactive chart showing contributions vs interest earned
Multiple Frequencies
Daily, monthly, quarterly, or annual compounding
Calculate Compound Interest
Enter your savings details to see how compound interest grows your money over time.
How Compound Interest Works
The Compound Interest Formula
Where P is the principal, r is the annual rate, n is the compounding frequency per year, t is years, and PMT is the regular contribution. Unlike simple interest (which only grows linearly), compound interest earns interest on previously earned interest — creating exponential growth.
Simple vs Compound Interest
With simple interest, a £10,000 deposit at 7% earns £700 every year — always £700. With compound interest, you earn £700 in year one, then £749 in year two (7% of £10,700), then £801.43 in year three, and so on. After 30 years, simple interest gives you £31,000 while compound interest gives you over £76,000.
The Power of Compounding Over Time
Short-Term Savings (1-5 years)
Over short periods, the difference between simple and compound interest is modest. A £10,000 deposit at 5% earns roughly £2,763 with compounding over 5 years versus £2,500 with simple interest. The benefit is real but not dramatic.
Long-Term Wealth Building (20-30 years)
Over decades, compounding becomes extraordinary. £10,000 at 7% for 30 years grows to £76,123 — more than seven times your original deposit. Add £200 monthly contributions and the total reaches over £320,000, with more than half coming from interest alone.
How to Use This Compound Interest Calculator
Enter Your Starting Amount
Your initial deposit or current savings balance.
Set Contributions & Rate
Add your monthly contribution and expected annual rate.
See Your Projected Growth
Instantly view your balance, chart, and year-by-year breakdown.
Tips for Maximising Compound Interest
- Start early. Time is the most powerful factor in compounding. Starting 10 years earlier can double your final balance, even with the same contributions.
- Increase contributions over time. As your income grows, increase your monthly contributions. Even small increases compound significantly over decades.
- Reinvest returns. Whether dividends, interest, or capital gains — reinvesting keeps the compounding engine running at full speed.
- Choose higher compounding frequency. Monthly compounding earns slightly more than annual. Daily earns slightly more than monthly. When comparing savings accounts, check the AER for a true comparison.
Want deeper insights?
ARIA analyses your entire portfolio with institutional-grade risk management, position sizing, and optimisation. See how your real investments compound — not just projections.
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