UK Savings Calculator

See how regular saving grows over time with compound interest — and how much of your final pot is growth rather than the money you put in. Includes an inflation-adjusted view in today's pounds.

Your saving plan

Starting balance

Monthly saving

Annual interest / return

Time horizon

20 years

Adjust for inflation

Annual inflation rate

Estimated balance after 20 years

£—

You saved£—

Interest / growth£—

Contributions Interest / growth

Show yearly breakdown

Year	Contributions	Interest	Balance

Educational estimate — not financial advice. Interest and returns vary and are not guaranteed. For tax-free growth, see the ISA Calculator.

How it works

Enter your starting balance, how much you save each month, an assumed annual interest or return rate, and how many years you plan to save. The calculator shows your estimated final balance, split into what you saved and the interest/growth earned on top. Turn on inflation to see the same pot expressed in today's pounds.

Interest is compounded monthly, with savings assumed to be added at the end of each month — the same convention as the ISA Calculator.

Example calculation

You start with £1,000, save £250 a month, earn 5% a year and save for 20 years:

You save: £1,000 + £250 × 240 = £61,000
Estimated balance: ≈ £105,471
Interest earned: ≈ £44,471
At 3% inflation, that pot would buy roughly £58,400 in today's money.

Example assumes constant 5% return with no fees or tax. Real results vary.

Methodology & formula

With monthly compounding and end-of-month savings, the future value is:

FV = P(1 + r/12)^12t + M × [ (1 + r/12)^12t − 1 ] / (r/12)

P = starting balance
M = monthly saving
r = assumed annual rate (as a decimal)
t = number of years

Inflation adjustment: the nominal future value is divided by (1 + inflation)^t, and each year's contributions are discounted back to today's pounds, so the “real” figures show purchasing power, not a nominal pot.

Assumptions: constant rate, no fees, no withdrawals, monthly compounding, contributions at month-end.

UK-specific information

Savings interest can be taxable. In 2026/27 the Personal Savings Allowance lets basic-rate taxpayers earn up to £1,000 of interest tax-free (£500 for higher-rate, £0 for additional-rate). Anything above this is taxed at your income tax rate. GOV.UK · 2026/27
ISAs keep interest and growth tax-free. Money in an ISA is not counted against your Personal Savings Allowance at all. If you're a higher-rate taxpayer, an ISA is often the more efficient home for savings.
Savings accounts vs investments: cash savings aim to protect your money; investments (e.g. inside a Stocks & Shares ISA) carry risk of loss but have historically grown more over the long term. Neither is guaranteed.

Frequently asked questions

Is savings interest taxed in the UK?

It depends on your other income and your Personal Savings Allowance (2026/27: £1,000 for basic-rate, £500 for higher-rate, £0 for additional-rate taxpayers). Interest inside an ISA is always tax-free.

What's the difference between this and the ISA Calculator?

This calculator models general saving. The ISA Calculator models money inside the UK's tax-free ISA wrapper — including the Lifetime ISA 25% bonus and your £20,000 annual allowance.

Should I adjust for inflation?

It helps you see the real purchasing power of your future pot. If inflation averages 3% a year, a £100,000 nominal pot in 20 years would buy roughly what £55,000 buys today.

Can I use this for investments too?

Yes — use a higher assumed return (e.g. 5–7%) to model long-term investing. Remember that investments can fall in value, and returns are not guaranteed.

Why does the result show “growth share”?

It's the percentage of your final balance that came from interest or growth rather than the money you saved. A higher rate or longer horizon increases this share.

Related calculators

ISA Calculator · Home · Methodology

Sources

GOV.UK — Tax on savings interest: gov.uk/apply-tax-free-interest-on-savings (accessed 2026, 2026/27 rates)
GOV.UK — Individual Savings Accounts (ISAs): gov.uk/individual-savings-accounts (accessed 2026)

Casvia provides educational calculators and general information. It does not provide personal financial, tax or investment advice. Rules and thresholds can change — always check the latest official guidance.