Figures are illustrative only, ignore charges and tax, and are not a forecast or personal recommendation.
This calculator answers the question at the heart of retirement planning: based on my current age, savings, and contributions, will I have enough to fund the retirement income I want — or is there a shortfall to close? It projects your likely pension pot at retirement, works out roughly how large a pot you'd need to sustainably fund your desired income, and shows the gap between the two.
How the calculation works
First, the calculator projects your pot at retirement using your current savings, monthly contributions, and assumed investment return, over the number of years until your target retirement age — the same method used in our Retirement Calculator. Second, it takes your desired annual retirement income (entered in today's money) and inflates it forward to your retirement date using your inflation assumption, since an income figure that feels right today will need to be higher in future pounds to buy the same amount. Third, it applies the 4% rule in reverse — dividing that inflated income figure by 0.04 — to estimate the size of pot required to sustainably support it. The difference between your projected pot and this required pot is shown as a shortfall (if negative) or surplus (if positive).
Why the required pot looks so large
Many people are surprised the first time they see this calculation: a desired income of £25,000 a year requires a pot of roughly £625,000 under the 4% rule (before adjusting for inflation over the years until retirement), because the pot needs to be large enough to sustainably provide that income for a retirement that could last 25-30+ years. If the State Pension will cover part of your desired income, subtract its value from your "desired annual income" field first, since this calculator projects only private savings.
Worked example
Someone aged 35, retiring at 65 (a 30-year horizon), with £30,000 saved and contributing £400 a month at an assumed 5% return, wanting £25,000 a year in today's money with 2.5% assumed inflation, will see their inflation-adjusted required income rise considerably by retirement, pushing the required pot well above £1 million in future pounds — and depending on their current trajectory, a meaningful shortfall against their projected pot. Adjusting the monthly contribution upward in the calculator shows immediately how much extra saving would be needed to close that gap.
What to do if there's a shortfall
A shortfall isn't a crisis — it's information. The main levers are contributing more each month, working a few years longer (which both adds contributions and gives more time to compound, and shortens the retirement the pot needs to fund), accepting a somewhat lower retirement income, or taking a higher-growth investment approach earlier in the plan (with correspondingly higher risk). Consolidating old pensions can also help you see the full picture more clearly — see our guide on SIPP versus workplace pension consolidation.
Frequently asked questions
Is the 4% rule reliable for working out how much I need?
It's a widely used rule of thumb based on historical data, not a guarantee — see our Pension Income Calculator for more on withdrawal rates and their limitations.
Should I include my ISA savings as well as my pension?
Yes, if you plan to use ISA savings to help fund retirement — enter your combined pension and ISA balances and contributions for a fuller picture, though remember pension and ISA withdrawals are taxed differently.
What if I get a shortfall but I'm decades from retirement?
A shortfall projected decades in advance is far easier to close than one spotted a few years before retirement — small increases to contributions made early benefit from many more years of compounding.
Does this account for downsizing or other retirement income sources?
No — it only projects the specific savings and contributions you enter. Property, inheritance, or other expected income should be considered separately alongside this figure.
Common mistakes when assessing a shortfall
A frequent mistake is entering a desired income figure that doesn't reflect how spending actually tends to change in retirement — many people spend less on commuting, work clothes, and pension contributions themselves once retired, but more on leisure, travel, or eventually care. Rather than guessing, it can help to build a rough retirement budget first (using current spending as a starting point, adjusted for expected changes) before entering a desired income figure here.
A second mistake is treating a calculated shortfall as fixed and unchangeable, when in fact this calculator is designed to be adjusted repeatedly. Small changes to contributions, retirement age, or the assumed return can shift the result significantly — the most useful way to use this tool is to try several realistic combinations (a higher contribution, a slightly later retirement age, or both) rather than treating the first result as final.
Is the 4% rule too conservative or too aggressive for UK retirees?
It was derived largely from historical US market data over 30-year periods, and views differ on how directly it applies to UK investors and to retirements of different lengths — many UK planners treat it as a reasonable starting reference point rather than a precise target, and increasingly favour flexible, review-based withdrawal approaches instead.
Does this calculator factor in the State Pension?
No — it projects private pension and savings provision only. Since the State Pension provides a separate, broadly inflation-linked income from State Pension age, you can reduce your entered "desired annual income" figure by your expected State Pension amount to get a more accurate picture of the private shortfall specifically.
What if closing the shortfall would require an unrealistically high monthly contribution?
This is useful information in itself — it may point toward a combination of smaller changes (contributing somewhat more, retiring a little later, and accepting a modestly lower income) being more realistic than relying on any single lever alone to close a large gap.
Should I recalculate this every year?
Yes, ideally — contributions, investment performance, income goals, and even inflation expectations all change over time, so an annual check-in keeps the shortfall or surplus figure meaningfully up to date rather than working from assumptions that were accurate several years ago.