About CompoundCalc

What We Do

CompoundCalc is a free online compound interest calculator designed to help you understand how your savings and investments grow over time. Whether you're exploring the basics of compound interest, planning for retirement, or modelling a specific savings scenario, our calculator provides clear, instant projections with detailed year-by-year breakdowns.

We also publish educational guides and worked examples to help you make better financial decisions. Our content covers everything from the Rule of 72 to the practical differences between compounding frequencies.

Our Methodology

The calculator uses the standard compound interest formula: A = P(1 + r/n)^nt, where P is the principal, r is the annual rate, n is the compounding frequency, and t is time in years. Regular contributions are distributed evenly across compounding periods and added before each period's interest calculation.

This is the same formula used by banks, building societies, and financial institutions worldwide. The calculations are performed entirely in your browser using JavaScript — there is no server-side processing, rounding adjustments, or hidden modifications. The source code is transparent and the results are reproducible with any scientific calculator.

Data Sources and Accuracy

Reference interest rates mentioned in our guides and scenarios are sourced from the Bank of England, major UK banks' published rates, and the Office for National Statistics. We review and update these figures regularly, though rates change frequently and should always be verified with the relevant financial institution.

The calculator produces mathematically precise results for the given inputs. However, real-world outcomes depend on many factors not captured by the formula: fluctuating rates, taxes, fees, inflation, and market volatility. Our results are estimates for planning and educational purposes, not predictions of actual returns.

Privacy

We take your privacy seriously. All calculations happen entirely in your browser — no financial data, personal information, or calculation results are transmitted to our servers or any third party. If you choose to save your inputs using the "Save" feature, that data is stored in your browser's localStorage only and never leaves your device.

We use Google Analytics and Google AdSense, both of which are subject to Google's privacy policies and our consent management. You can manage your privacy preferences at any time. For full details, see our Privacy Policy.

Not Financial Advice

CompoundCalc is an educational tool. We do not provide personalised financial advice, investment recommendations, or professional services of any kind. The information on this website is for general informational purposes only and should not be relied upon as a substitute for professional advice.

Before making any financial decisions — including choosing savings accounts, making investments, or adjusting pension contributions — please consult a qualified, independent financial adviser who can consider your individual circumstances. See our Terms of Use for the full disclaimer.

Contact

Have a question, found a bug, or want to suggest an improvement? We'd love to hear from you. Use our contact form or email us at [email protected].