Enter your savings balance, monthly spending, and interest rate to find out exactly how long your money will last — with a full month-by-month breakdown and plain-English explanation of your result.
6 min readUpdated April 2026🌐 Generic · 🇬🇧 UK · 🇺🇸 US
Choose your locale, enter your figures, and see exactly how long your money will last.
Mode
Your Savings
£
Your current savings balance
£
How much you spend or withdraw each month
Interest & Inflation
% AER
Rate paid on your savings account
% p.a.
Set to 0 to ignore inflation, or enter expected CPI
Money Lasts
—
Until balance hits zero
End Date
—
Projected depletion date
Total Interest
—
Earned over the period
Total Withdrawn
—
Net payments to yourself
Savings Balance Over Time
Month-by-Month Breakdown
First 24 months shown — click to expand
Month
Opening Balance
Interest Earned
Withdrawal
Closing Balance
Formula & How It Works
How is your savings runway calculated?
The core question — how long will my savings last if I withdraw monthly? — is answered using the present value of an annuity formula, rearranged to solve for time. The formula looks like this:
n=−ln(1−r×PV÷PMT) ÷ ln(1+r)
Each variable has a specific meaning. n is the number of months your savings last. PV (present value) is your starting savings balance. PMT is your monthly withdrawal amount — the payment you take from the pot each month. r is the monthly interest rate, which is your annual interest rate divided by 12 and then by 100 — so a 3% annual rate becomes 0.0025 per month. The ln is the natural logarithm, a standard mathematical function available in any calculator or spreadsheet.
Two important special cases exist. First, if the interest rate is zero — you're keeping cash under the mattress — the formula simplifies to n = PV ÷ PMT. A £50,000 pot with £1,500 monthly withdrawals and zero interest lasts exactly 33.33 months, or 2 years and 9 months. Second, if your savings account earns more in monthly interest than you withdraw — in other words, if PV × r ≥ PMT — your balance never reaches zero. The interest replenishes what you spend, and the balance either holds steady or grows.
How is inflation handled?
When you enter an inflation rate, the calculator switches to an iterative month-by-month simulation rather than the closed-form formula above. Each month's withdrawal increases by the inflation rate divided by 12. This reflects the real-world experience of needing more money each year just to buy the same things — which means your savings depletion calculator result in nominal terms may look longer than the inflation-adjusted reality. A withdrawal of £1,500 today needs to be roughly £1,645 in five years just to maintain the same standard of living at 2% annual inflation.
A practical example: Karen from Leeds
Karen is a 62-year-old retired secondary school teacher from Leeds. She has taken her Teachers' Pension early at a reduced rate and receives £820 per month from it. Her monthly expenses total £2,100. This means she needs to draw down £1,280 per month from her savings to bridge the gap until her State Pension kicks in at age 67. Karen has £75,000 in a fixed-rate Cash ISA earning 4.2% AER.
Plugging Karen's numbers into the formula: r = 4.2 ÷ 12 ÷ 100 = 0.0035 per month. The monthly interest earned on £75,000 is £262.50 — significantly less than her £1,280 withdrawal, so the pot will deplete. Using the formula: n = −ln(1 − 0.0035 × 75,000 ÷ 1,280) ÷ ln(1.0035) = −ln(0.7949) ÷ 0.003494 ≈ 65.5 months, or 5 years and 5 months. Karen's savings will last until she is approximately 67 years and 5 months old — just past her State Pension age of 67, meaning her money lasts long enough for the State Pension to take over. If she were withdrawing £1,500 instead, the runway shrinks to 54 months — just 4 years and 6 months, leaving a gap before her State Pension starts. This illustrates why understanding how long will my money last in retirement UK is so important for planning.
For more complex scenarios involving variable investment returns and sequence-of-returns risk, the Retirement Drawdown Simulator offers a more stress-tested view of pension pot longevity.
Key Assumption
This calculator assumes a fixed, constant interest rate throughout the period. In practice, savings rates change — particularly for easy-access accounts that track the Bank of England base rate. For fixed-rate bonds or ISAs with a locked-in term, this assumption is accurate. For variable accounts, the actual runway may be shorter or longer than calculated.
Interpreting Your Result
What does my savings runway result mean?
If your result shows a number of years and months, that is the time until your savings balance reaches zero at the current withdrawal rate and interest rate. If the calculator shows "Never runs out", it means your account interest each month matches or exceeds your monthly withdrawal — your savings are self-sustaining at that rate. This is the point financial planners call a retirement savings runway becoming infinite, and it is the goal underpinning strategies like FIRE (Financial Independence, Retire Early).
Understanding how long will my money last with interest is one of the most important retirement planning questions you can ask. Many people are surprised to find how much difference even 1% of interest makes over a multi-year drawdown. On a £100,000 pot with £1,500 monthly withdrawals, the difference between 0% and 4% interest is over three extra years of runway.
If the result is less than five years and you plan to rely heavily on these savings, that is a signal to revisit your withdrawal rate, explore additional income sources, or consider how your State Pension entitlement might reduce the gap.
How can I make my money last longer in the UK?
The interest rate your savings earn has an outsized effect on the result. Moving from a current account earning 0% to a competitive Cash ISA earning 4–5% AER can add years to your savings runway. UK savers have several tax-efficient options that extend the pot further:
Account Type
2026 Rate / Benefit
Best For
Cash ISA
Up to 5.1% AER (easy access)
Tax-free interest; counts toward £20,000 annual ISA allowance
NS&I Premium Bonds
Prize-equivalent ~4% (variable)
Tax-free winnings; FSCS-equivalent security as backed by HM Treasury
Fixed-Rate Savings Bond
Up to 5.3% AER (1–2 year)
Predictable income; interest taxed but within Personal Savings Allowance
Easy-Access Savings Account
Up to 5.2% AER
Flexibility; interest within £500–£1,000 Personal Savings Allowance
The FSCS (Financial Services Compensation Scheme) protects up to £85,000 per person, per institution. If your savings pot exceeds this, spreading funds across multiple FSCS-protected banks or building societies protects the full amount. NS&I is backed directly by HM Treasury, making it effectively unlimited in protection — a consideration for those with larger balances.
How does the State Pension affect how long my savings last?
The full new State Pension for 2026/27 is £11,502.40 per year (£958.53 per month), paid from age 66 (rising to 67 between 2026–2028). For most UK retirees drawing from savings, the State Pension acts as a floor income that significantly reduces the required monthly withdrawal. Using the example above: if your expenses are £2,000 per month and the State Pension covers £958, you only draw £1,042 from savings — potentially doubling or tripling the savings runway compared to a scenario without any pension income. Use the monthly withdrawal field to enter only the gap between your total expenses and any pension or other income you receive.
Common mistakes to avoid
The most frequent error is not accounting for inflation. A withdrawal of £1,500 today will feel like considerably less in purchasing power terms in ten years if inflation averages 2–3% annually. Use the inflation rate field in the calculator to model the real runway. The second common mistake is overestimating interest rates. Many savings accounts — particularly current accounts and instant-access accounts at high-street banks — pay well below 1%. Using a 4% rate in the calculator but keeping money in an account paying 0.5% will give a wildly optimistic result. The third mistake is forgetting lump-sum expenditures: a car purchase, home repair, or holiday can materially reduce the balance and shorten the runway in ways a fixed monthly model won't capture. Consider running the calculator with a reduced opening balance to account for planned large expenses.
For a more complete picture of retirement readiness — including investment growth and Coast FIRE scenarios — the FIRE Calculator and the Compound Interest Calculator are natural companions to this tool.
Frequently Asked Questions
How long will my savings last if I withdraw monthly?
It depends on three variables: your starting balance, your monthly withdrawal, and the interest rate your savings earn. Use the formula n = −ln(1 − r × PV ÷ PMT) ÷ ln(1 + r), where r is the monthly interest rate, PV is your balance, and PMT is your monthly withdrawal. If your savings account earns more in interest each month than you withdraw, the money never runs out. This calculator does all the maths instantly and produces a month-by-month chart so you can see exactly when the balance hits zero.
How long will £100,000 last in retirement?
At £1,000 per month withdrawal and 3% AER interest, £100,000 lasts approximately 10 years and 5 months. At £1,500 per month, it lasts around 6 years and 3 months. At £2,500 per month with no interest, just 3 years and 4 months. Adding the UK State Pension (£958/month in 2026/27) as income that reduces your required monthly withdrawal can dramatically extend the runway — if your expenses are £2,500 but the State Pension covers £958, you only need to draw £1,542 from savings. Always enter your net withdrawal requirement, not your total expenses, for the most accurate result.
How long will £50,000 last if I spend £1,500 a month?
With no interest, £50,000 at £1,500 per month lasts exactly 33 months — 2 years and 9 months. At 3% AER, it lasts approximately 35 months — around 2 extra months from interest earnings. At 5% AER, the runway extends to roughly 36 months. For UK savers, holding the £50,000 in a Cash ISA currently earning around 4.5–5% AER would meaningfully extend the runway and keep all interest tax-free within the £20,000 annual ISA allowance (with any overflow in a Personal Savings Allowance-eligible account).
What is the formula for working out how long savings will last?
The formula is: n = −ln(1 − r × PV ÷ PMT) ÷ ln(1 + r). Here, n is the number of months, r is the monthly interest rate (annual rate ÷ 1200), PV is your starting balance, and PMT is your monthly withdrawal. If r = 0, simplify to n = PV ÷ PMT. If the monthly interest earned (PV × r) is greater than PMT, the savings never deplete. This is the standard annuity depletion formula used in actuarial and financial planning work. Spreadsheet users can replicate it using the NPER function: =NPER(rate, −PMT, PV).
How long will my money last in retirement in the UK?
For UK retirees, the full new State Pension of £11,502.40 per year (£958.53 per month) paid from age 66 reduces the required monthly savings withdrawal significantly. Enter only the gap between your monthly expenses and your pension and other income into the "Monthly Withdrawal" field for an accurate result. UK savers also benefit from tax-free interest in Cash ISAs (up to £20,000 per year), which can improve the effective interest rate and extend the runway. The FSCS protects savings up to £85,000 per institution, and NS&I products are backed by HM Treasury with no cap.
How long will my savings last if I'm self-employed in the UK?
Self-employed people in the UK often rely on savings as a buffer between contracts or during slow periods, and typically have no employer-backed pension, no statutory sick pay, and variable income. This makes an accurate savings runway calculation especially important. Financial advisers typically recommend self-employed workers hold 6–12 months of expenses in an accessible account. If you're drawing down savings during a gap in income, enter your total monthly expenses as the withdrawal amount. Remember that self-employed NI contributions (Class 2 and Class 4) and income tax are typically paid in January and July lump sums — factor these into your withdrawal rate or reduce your opening balance accordingly.
Is a savings depletion calculator the same as a drawdown simulator?
No — they serve related but different purposes. A savings depletion calculator (this tool) models a fixed balance, a fixed monthly withdrawal, and a fixed interest rate. It is ideal for cash savings, Cash ISAs, and fixed-rate accounts where the return is known. A retirement drawdown simulator models withdrawals from an invested portfolio subject to variable returns, inflation, and sequence-of-returns risk — where a bad run of markets early in retirement can deplete a portfolio even if the long-run average return looks healthy. If your savings are invested in a pension or stocks and shares ISA, visit the Retirement Drawdown Simulator for a more realistic stress-test of your retirement savings runway.
How long will my nest egg last if I earn interest on it?
Interest earned during the drawdown period meaningfully extends the life of your savings — particularly in the early years when the balance is highest and earning the most interest. A nest egg of £200,000 earning 4% AER and paying out £1,500 per month would last approximately 18 years and 8 months. The same pot with no interest runs out in 11 years and 1 month — over 7 years shorter. This demonstrates why placing your drawdown pot in the best available savings account is one of the most impactful decisions you can make. Even moving from 1% to 3% AER on a large balance adds several years to the runway.
Disclaimer: This calculator is provided for educational and informational purposes only and does not constitute financial advice. Results are based on the inputs you provide and assume fixed, constant interest rates and withdrawal amounts over time. Actual savings account rates vary and may change. Interest calculations are an approximation — real-world compounding terms vary by institution. UK tax rules, ISA limits, State Pension rates, and FSCS limits are stated as understood for 2026/27 and are subject to change. CalculatorDashboard.com is not a regulated financial adviser. Always consult a qualified financial adviser before making decisions about your retirement income or savings strategy.