UK Savings Calculator
Enter your starting balance, monthly contributions, interest rate and how long you plan to save. The calculator applies compound interest and shows your projected balance year by year on a chart.
Compound interest means you earn interest on your interest — the earlier you start, the more it works in your favour.
How the calculation works
We believe numbers should be transparent. Here is the formula behind this calculator.
Worked example
Worked example: £1,000 saved, £200/month
Important assumptions
- The interest rate is assumed to stay constant for the whole period.
- Interest is taxed depending on your Personal Savings Allowance (£1,000 for basic-rate, £500 for higher-rate taxpayers).
- Results are before inflation unless you adjust the rate yourself (see our inflation guide).
- This is a projection, not a guarantee — real returns vary.
Rates & official sources
Every calculation is based on the official rates and rules published by GOV.UK and HMRC.
Frequently asked questions
What is compound interest?
It is interest earned on both your original money and the interest you have already earned. Over long periods, compounding creates growth on growth, which is why starting early matters.
Should I use an ISA?
A Cash ISA shelters your interest from tax completely (you get an allowance each tax year). If you are saving for retirement, a workplace pension adds employer contributions and tax relief on top.
Is this rate before or after tax?
The rate you enter is the gross rate. Interest tax depends on your income band and Personal Savings Allowance, so the after-tax result may be lower.
How do I calculate interest on savings?
The AER (annual equivalent rate) is the headline figure banks use to compare savings accounts. Enter the AER into this calculator along with your balance and monthly deposits, and it applies the interest each compounding period to the growing balance. Over a year, a £1,000 balance at 4% AER earns roughly £40 before tax.
Related calculators
Related guides
New to the topic? Read a plain-English guide on savings & investments, with worked examples and tips.
How compound interest works
The eighth wonder of the world, with real numbers.
Read the guide Personal FinanceHow much should I save?
A realistic savings target for your income and goals.
Read the guide Personal FinanceBuilding an emergency fund
Three to six months of costs — and how to get there.
Read the guide TaxCapital Gains Tax explained
How Capital Gains Tax works — the £3,000 allowance, the 18% and 24% rates, and when you pay it.
Read the guide TaxSavings interest tax explained
The Personal Savings Allowance and tax on savings interest — £1,000 for basic-rate, £500 for higher-rate, and what happens above.
Read the guideThese calculations are estimates for guidance only and are not professional financial, tax or legal advice. UK rates and rules change, so always verify important figures with official GOV.UK / HMRC information or speak to a qualified professional. See our full disclaimer.