Money tool
Savings & Compound Interest Calculator
Estimate savings growth from a starting balance, monthly deposits and your own annual rate, with UK and US currencies and a clear interest breakdown.
Savings assumptions and common questions
How is the interest calculated?
We convert the effective annual rate (AER in the UK, APY in the US) into an equivalent monthly rate: (1 + annual rate ÷ 100) raised to the power of 1/12, minus 1. Each month, interest is added to the balance and your monthly saving is added at the time you selected. Interest stays in the account and earns more interest.
We keep full precision during the calculation and round displayed money to two decimal places. Banks may calculate daily, use different rounding or credit interest at different times, so their figures may differ.
Is the rate guaranteed for the whole period?
No. This estimate holds your chosen rate and monthly saving constant. It does not model bonus periods, rate changes, deposit limits, withdrawals or tiered rates. Check your account terms, especially for regular-saver accounts.
Does this include tax or inflation?
No. Results are before tax and fees, and show future money without adjusting for rising prices. Currency selection does not apply tax rules. This is a savings illustration, not an investment forecast or financial advice.
How does the target option work?
We find the first month-end balance that reaches your target, up to 100 years. If you already have enough, the result says so. If your savings do not reach the target within that limit, we show that clearly instead of inventing a date.
Learn more: CFPB: how compound interest works and Yorkshire Building Society: savings rates and AER.
Processed privately in your browser — your entries are not uploaded.
Good to know
How this tool works
Estimate savings growth from a starting balance, monthly deposits and your own annual rate, with UK and US currencies and a clear interest breakdown. Work through the labelled controls, review the result in the preview and reset the tool whenever you want to begin again.
Frequently asked questions
What is Savings & Compound Interest Calculator useful for?
See your savings grow or find out how long it takes to reach a target. Try more than one realistic set of figures and verify important decisions with the relevant provider or adviser.
Is my information stored?
This tool works in your browser. The information you enter is not sent to us or saved in an account by this tool.
How accurate is the result?
The calculation follows the assumptions shown on the page. Rounding, provider methods and real-world charges can produce small differences.