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Compound Interest Calculator

See how a starting amount plus regular monthly contributions can grow over time through compounding — ideal for modelling an ISA or pension.

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Why compounding rewards patience

Each year’s growth earns its own growth the next year. Over decades this snowballs, which is why a Stocks & Shares ISA or pension started early can outgrow much larger contributions made later.

Frequently asked questions

Can I model an ISA?
Yes. Enter your starting balance and monthly contribution within your £20,000 annual ISA allowance, and an expected return, to project the future value tax-free.