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UK Savings Calculator

Updated August 2026 Savings & Investments GOV.UK help to save & ISAs

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.

Your details

Gross annual rate before tax

Results

Projected final balance
£31,038.96
After 10 years
Money you put in
£25,000.00
Interest earned
£6,038.96
Growth multiple
1.24×

Your savings growth over time

31,039
1,000
£1,000Year 5£31,039

How the calculation works

We believe numbers should be transparent. Here is the formula behind this calculator.

Final balance = contributions + interest, where interest is applied to the growing balance each compounding period

Worked example

Worked example: £1,000 saved, £200/month

Start: £1,000. You save £200 a month for 10 years = £25,000 in total contributions.
At 4% interest added monthly, the balance grows to roughly £31,000.
That means about £6,000 of your total is interest you earned just by leaving the money in place.

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.

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.

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Related guides

New to the topic? Browse the guides section for plain-English explainers on savings & investments, including worked examples and tips.

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These 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.