Savings Calculator
Calculate how your UK savings will grow over time with regular deposits, AER, and compound interest. ISA, easy-access, notice and fixed-rate bond projections.
How Savings Grow With Regular Deposits and Interest
The honest answer to whether a Cash ISA or an easy-access savings account grows your money faster in 2025 is: it depends on how much interest you earn and how much tax you'd otherwise pay on it. Headline AERs on the two products are now broadly similar — both sit in the 4% to 5% range tracked by Bank of England quoted rates and aggregators like MoneySavingExpert — so the deciding factor is usually the Personal Savings Allowance. A basic-rate taxpayer can earn £1,000 of savings interest tax-free each year, a higher-rate taxpayer £500, and an additional-rate taxpayer £0. Once you breach that threshold, every extra pound of interest is taxed at your marginal rate, which is exactly the situation a Cash ISA — where interest is sheltered for life — is designed to solve.
This savings calculator projects future balances for any UK savings product that quotes an AER, including easy-access accounts, notice accounts, fixed-rate bonds, regular savers, Cash ISAs and Lifetime ISAs (without the bonus, which the compound interest calculator handles separately). It uses the same compound interest formula your bank uses to derive the AER it advertises, so the figures line up with the projections in your online banking dashboard. Enter your starting balance, your monthly deposit, the quoted AER, and the number of years you plan to save. The result is a realistic future value rather than an aspirational one.
Where this calculator differs from generic global tools is in the UK context layered around the maths. The 2025/26 ISA allowance is £20,000 across all your ISAs combined, the FSCS protects £85,000 per person per banking licence (£170,000 for joint accounts), and savings interest has been paid gross — without tax deducted at source — since April 2016, which makes you, not the bank, responsible for declaring it to HMRC if you exceed your allowance. Use the calculator to plan around those numbers rather than ignoring them.
How to Project Your Savings Over Time
Enter your opening balance, monthly contribution, the AER quoted by the savings account, and how many years you plan to save. The calculator returns the projected future value, the total of your contributions, and the interest earned on top — all using the standard compound interest formula UK banks use to quote AER.
- Enter your opening balance — the cash you already hold in the account on day one.
- Add your planned monthly contribution. For a regular saver, this is the fixed monthly amount; for an ISA, keep the annual total under £20,000.
- Type the AER quoted by the account, exactly as advertised (e.g. 4.65 for an account paying 4.65% AER).
- Set the number of years you intend to save — 1 to 5 years for fixed bonds, longer for ISAs and pension-adjacent goals.
- Click Calculate. The output shows projected future value, the total of your contributions, and interest earned, with monthly compounding applied by default.
- Re-run the projection any time the BoE base rate moves and your bank passes the change on, or when you switch products.
The Future Value of Savings Formula
The formula used: FV = P(1 + r/n)^(nt) + PMT × [((1 + r/n)^(nt) - 1) / (r/n)] where P = initial deposit, PMT = monthly contribution, r = AER as a decimal, n = compounding periods per year, t = years
UK banks quote savings rates using the Annual Equivalent Rate, or AER. This is a regulated figure designed to make accounts comparable regardless of how often interest is added — daily, monthly, quarterly or yearly. Two accounts paying the same nominal rate but with different compounding frequencies will quote different AERs, and the higher AER is genuinely the better deal.
FV = P(1 + r/n)^(nt) + PMT × [((1 + r/n)^(nt) - 1) / (r/n)]
P is your opening balance. PMT is the regular monthly contribution. r is the AER expressed as a decimal (4.5% becomes 0.045). n is the number of compounding periods per year (12 for monthly, the most common for UK savings). t is the term in years. The first half of the formula tracks the growth of your opening balance, and the second half adds the future value of every monthly deposit you'll make over the term.
Because AER already bakes in compounding, the calculator can use it directly without you having to convert from a gross nominal rate. That's a useful contrast with US APR-based products — under FCA rules, AER must reflect what you'd actually receive if you left the money in for a full year, including the effect of interest paid more frequently than annually. Per Bank of England quoted rates, easy-access products typically compound either monthly or daily, while fixed bonds often pay interest at maturity but still quote AER for comparability.
Savings Growth Examples: £100, £250, and £500 Per Month
Paying £200 a month into an easy-access savings account at 4.5% AER for 2 years on top of a £500 opening balance grows to roughly £5,562 — that's £5,300 of your own money plus around £262 of interest, all sheltered inside the £85,000 FSCS limit if held with one banking licence.
Emergency fund — £200/month into easy-access at 4.5% AER for 2 years
P = 0, PMT = 200, r = 0.045, n = 12, t = 2. FV = 200 × [((1.00375)^24 - 1) / 0.00375]
Future value ≈ £5,011. Contributions = £4,800. Interest earned ≈ £211. Comfortably under the FSCS £85,000 limit and inside the basic-rate Personal Savings Allowance even at higher rates.
House deposit — £500/month into a Cash ISA at 4.7% AER for 5 years
P = 0, PMT = 500, r = 0.047, n = 12, t = 5. FV = 500 × [((1.003917)^60 - 1) / 0.003917]
Future value ≈ £33,820. Contributions = £30,000. Interest earned ≈ £3,820. All interest is tax-free inside the ISA wrapper and uses £6,000 of the £20,000 annual ISA allowance each year.
First-home Lifetime ISA proxy — £100/month at 5% AER for 8 years (excluding 25% government bonus)
P = 0, PMT = 100, r = 0.05, n = 12, t = 8. FV = 100 × [((1.004167)^96 - 1) / 0.004167]
Future value ≈ £11,769 in interest-bearing growth. Contributions = £9,600. The 25% LISA government bonus would add up to £2,400 on top of contributions — model that part with the compound interest calculator.
Mid-term saving — £10,000 lump sum into a 3-year fixed-rate bond at 4.8% AER
P = 10000, PMT = 0, r = 0.048, n = 12, t = 3. FV = 10000 × (1.004)^36
Future value ≈ £11,547. Interest earned ≈ £1,547. Locked away for 3 years with no easy-access. Held with a single banking licence, the deposit and accumulated interest stay under the £85,000 FSCS protection ceiling.
Help to Save — £50/month for 4 years with the 50% government bonus
P = 0, PMT = 50, r = 0, n = 12, t = 4. Contributions = 50 × 48 = £2,400. Bonus = 50% of highest balance reached = up to £1,200.
Maximum payout ≈ £3,600 (£2,400 contributions plus £1,200 government bonus). Eligibility runs through Universal Credit or Working Tax Credit; the bonus is paid at year 2 and year 4. Per MoneyHelper, this is one of the highest-return savings vehicles available to lower-income UK households.
When to Model Your Savings Goals
Run the numbers any time you're sizing a savings goal, comparing two products with different AERs, or deciding whether to switch when your bank's variable rate drifts below the rest of the market. Goal planning is the most common use — pick a target (a 10% house deposit, a £5,000 emergency fund, a £3,000 wedding budget) and work backwards to a monthly contribution that gets you there inside your timeline. The calculator is also useful before opening a fixed-rate bond, because the locked-in AER lets you project a near-certain future value rather than an estimate.
Rate switching is the second big trigger. UK easy-access rates have moved sharply with the Bank of England base rate over the last few years; a competitive 4.7% AER from 2024 can quietly slip to 3.5% if the bank doesn't pass on cuts evenly, and the calculator quickly shows what that costs you over five years. The third trigger is ISA decision-making each tax year — running the projection for a Cash ISA versus an easy-access savings account, with the Personal Savings Allowance baked in, often tips the answer toward the ISA for higher-rate taxpayers and toward easy-access for basic-rate taxpayers who'll never breach £1,000 of interest.
One final use is reality-checking against the broader UK savings landscape. The ONS Household Saving Ratio sits in the 5% to 10% range in normal years (it spiked during COVID and has since reverted), and the FCA Financial Lives Survey consistently finds the median UK adult holds under £1,000 in accessible savings. If your projected balance materially beats those benchmarks, you're ahead of the curve; if not, the calculator quantifies the gap so you can close it.
Savings Account Terms Explained
Easy-Access vs Notice vs Fixed Rate Bonds: Trade-offs Compared
The three mainstream UK savings product categories trade access for rate. Easy-access accounts let you withdraw at any time but usually pay the lowest AER. Notice accounts force a delay before withdrawal in exchange for a modest premium. Fixed-rate bonds lock your money up entirely for the term and typically pay the highest rate when markets expect base rates to fall, or a similar rate to easy-access when markets expect them to rise.
| Product | Typical 2025 AER range | Access | FSCS protected? | Best for |
|---|---|---|---|---|
| Easy-access savings | ~4.0% – 5.0% | Instant withdrawal | Yes, £85k per licence | Emergency fund, short-term goals |
| Notice account (30–120 days) | ~4.2% – 5.3% | Withdraw after notice period | Yes, £85k per licence | Savings you don't expect to need urgently |
| Fixed-rate bond (1–5 years) | ~4.3% – 5.5% (rate-cycle dependent) | Locked for full term | Yes, £85k per licence | Mid-term goals with a known date |
| Cash ISA (easy-access or fixed) | ~4.0% – 5.0% | Varies by ISA type | Yes, £85k per licence | Higher-rate taxpayers, anyone exceeding PSA |
| Premium Bonds (NS&I) | Prize fund rate ~4.0% – 4.5% (no guaranteed interest) | Cash out within ~3 working days | HMG-backed (effectively unlimited) | Tax-free luck-based returns, high deposit savers above FSCS |
Ranges quoted reflect the broad market per MoneySavingExpert and Bank of England quoted rates aggregates and shift with the BoE base rate, which sat in the 4% to 5% band through 2025. Always check current best-buy tables before opening any account — headline AERs change weekly.
Strategies to Build Savings Faster
- By age 30, a common guideline is to have the equivalent of 6 months' essential outgoings saved as accessible cash — typically £6,000 to £15,000 depending on living costs. This is a guideline, not a rule, and tracks the FCA's recommendation rather than any statutory target.
- By age 40, financial planners often suggest savings plus pensions roughly equal to your annual gross salary. Cash savings alone should comfortably cover 6 months' expenses with extra set aside for medium-term goals like a house deposit or car replacement.
- By age 50, aim for cash savings covering at least 6 months' outgoings plus 3 to 5 times your salary held across pensions and investments. The cash element acts as a buffer so you don't have to draw from invested assets during a market downturn.
- By state pension age, the PLSA Retirement Living Standards suggest a single person needs roughly £14,400/yr (minimum), £31,300/yr (moderate) or £43,100/yr (comfortable) in income — work backwards from those figures and use the retirement calculator to size the pot needed.
- Use the £20,000 ISA allowance every tax year if you can — it's a use-it-or-lose-it allowance and unused capacity doesn't roll forward.
- If you're eligible for Help to Save (on Universal Credit or Working Tax Credit), the 50% bonus is mathematically the highest-return savings vehicle available in the UK — prioritise it before any other savings product.
Savings Projection Mistakes to Watch For
- Holding more than £85,000 with one banking licence — anything over the FSCS limit is unprotected if the bank fails. Spread balances across separate licences (not just brands) for full protection.
- Mistaking 3 months' expenses for an adequate emergency fund. The MoneyHelper and Citizens Advice consensus is 3 months minimum for a dual-income household with stable jobs, and 6 months for single earners, the self-employed, or anyone in a volatile sector.
- Ignoring the Personal Savings Allowance. Higher-rate taxpayers with more than around £11,000 in savings at 4.5% will breach the £500 PSA and start losing interest to tax — at which point a Cash ISA almost always wins.
- Treating Premium Bonds as a guaranteed-interest product. The NS&I prize fund rate is an average across all bondholders; most savers earn less than the headline rate, while a tiny minority win large prizes.
- Locking funds into a long fixed-rate bond when you might need access. Early withdrawal penalties on fixed bonds can wipe out months of interest, and the FSCS doesn't help because the money isn't lost — it's just inaccessible.
- Forgetting that the 2025/26 ISA allowance of £20,000 is shared across all ISA types you hold, not £20,000 per ISA.
Savings Calculator: Common Questions Answered
How much interest can I earn on UK savings before paying tax?
Basic-rate taxpayers can earn £1,000 of savings interest tax-free each year under the Personal Savings Allowance. Higher-rate taxpayers get £500, and additional-rate taxpayers get £0. ISA interest doesn't count toward this allowance — it's tax-free indefinitely. Above the PSA, interest is taxed at your marginal rate.
Is my money safe in a UK savings account?
Yes, up to £85,000 per person per banking licence under the FSCS — £170,000 for joint accounts. Critically, this is per licence not per brand. Halifax and Bank of Scotland share one licence, for example, so balances are combined for FSCS purposes. Spread larger sums across separate licences.
Should I choose a Cash ISA or an easy-access savings account?
If you're a higher-rate taxpayer or expect to earn more than your Personal Savings Allowance in interest, a Cash ISA almost always wins because all interest is tax-free. For basic-rate taxpayers with modest balances who'll never breach £1,000 of interest, a higher-AER easy-access account often beats an ISA on raw return.
What is the 2025/26 ISA allowance?
£20,000 per tax year, shared across all ISA types you hold (Cash ISA, Stocks & Shares ISA, Innovative Finance ISA, and Lifetime ISA contributions of up to £4,000). It's a use-it-or-lose-it allowance — unused capacity doesn't roll forward to the following tax year.
How big should my emergency fund be?
The MoneyHelper and Citizens Advice consensus is 3 months' essential outgoings as a minimum — covering rent or mortgage, bills, food and travel. Aim for 6 months if you're self-employed, a single earner, or in an unstable sector. The FCA Financial Lives Survey shows most UK adults fall well short of either benchmark.
Do I have to declare savings interest on my tax return?
Banks pay savings interest gross since April 2016 and report it to HMRC. If your interest exceeds your Personal Savings Allowance, HMRC usually adjusts your tax code to collect the tax owed. If you complete Self Assessment, declare interest in the savings section. ISA interest never needs to be declared.
What is Help to Save and who's eligible?
Help to Save is a government-backed scheme paying a 50p bonus per £1 saved, up to £50/month for 4 years, giving a maximum bonus of £1,200. Eligibility is for adults receiving Universal Credit (with earnings above a threshold) or Working Tax Credit. The bonus is paid at the end of years 2 and 4 based on the highest balance reached.
Are notice accounts and fixed-rate bonds worth the loss of access?
Notice accounts typically pay 0.2 to 0.4 percentage points more than easy-access for the inconvenience of a 30 to 120 day notice period — usually only worth it for sums you're confident you won't need. Fixed-rate bonds pay more when markets expect base rates to fall, but penalties for early withdrawal can wipe out the rate premium.
How does AER differ from a gross interest rate?
AER is the standardised annual rate that includes the compounding effect of interest paid more often than yearly. A 4.4% gross rate paid monthly compounds to a slightly higher AER. UK banks must quote AER under FCA rules so accounts are directly comparable, regardless of how frequently they credit interest.
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