Compound Interest Calculator

Project investment growth with contributions and compounding.

Enter your details and select Calculate.

This tool provides an estimate. Verify results before making financial, educational or medical decisions.

Compound interest and investment growth

This guide explains how to use the calculator, includes an example, discusses limitations and answers common questions.

Compounding means interest or returns can themselves earn further returns. Over long periods, the assumed rate and contribution pattern have a large effect.

How to use this calculator

Enter the initial amount, assumed annual rate, duration and any contributions. The model applies the stated compounding schedule to estimate future value.

Worked example

£1,000 growing at 5% annually for 10 years becomes about £1,629 without additional deposits, before tax, fees or inflation.

When this calculator is useful

Useful for exploring savings, retirement and investment scenarios and comparing the effect of time.

When not to rely on it

Investment returns are not guaranteed and may be negative. Inflation, tax, fees and changing rates can materially reduce real outcomes.

Practical tip

Try several return assumptions rather than relying on one optimistic figure.

Frequently asked questions

Is compound interest guaranteed?

Bank interest depends on account terms; investment returns are uncertain.

Why does compounding frequency matter?

More frequent compounding can slightly change the effective annual return.

Does this show purchasing power?

Usually no. Adjust separately for inflation to estimate real value.

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Educational information only. Results are estimates unless otherwise stated. Verify important financial, medical or legal decisions with a qualified professional.