Retirement Savings Adequacy Calculator
See whether your current savings plan is on track to support the retirement income you want.
How this is calculated
Your current savings and monthly contributions are compounded forward at your expected annual return until retirement, giving a projected pot. That pot's sustainable monthly income is estimated using the 4% rule (4% of the pot per year, divided by 12). The gap between that and your desired income is your surplus or shortfall, and a month-by-month simulation of withdrawals in retirement (with the pot still earning your expected return) estimates how long the savings will actually last.
With this calculator's default inputs — starting at 30 with £20,000 saved, contributing £500/month at an expected 7% annual return until age 65 — 35 years of compounding growth does most of the work, which is why starting early matters more than the size of any single contribution. This projection assumes a constant average return every year; real portfolios don't grow smoothly, and a downturn early in retirement can do more lasting damage than the same-sized downturn later on (sequence-of- returns risk), which the simple month-by-month simulation here doesn't model. To see how a lump-sum contribution compounds on its own, or to solve backward from a target pot to the required monthly contribution, see the Compound Interest calculator, and to see what that pot is worth once inflation is accounted for, see the Inflation-Adjusted Return calculator.
Frequently asked questions
- What is the 4% rule?
- A common rule of thumb for retirement withdrawals: withdrawing 4% of your pot in the first year of retirement (then adjusting for inflation each year after) is historically unlikely to deplete the pot over a 30-year retirement. It's a guideline, not a guarantee — actual safe withdrawal rates depend on market returns, inflation and how long retirement lasts.
- How is "years savings will last" calculated?
- This simulates your pot in retirement month by month: it keeps earning your expected annual return, while your desired monthly income is withdrawn each month. If the withdrawal rate is below what the pot earns, it never depletes — the calculator shows this as no fixed end date.
- What does surplus or shortfall mean?
- The gap between the monthly income your projected pot would generate under the 4% rule, and the monthly income you said you want in retirement. A positive number means your projected savings comfortably support your desired income; a negative number means a gap you'd need to close with more savings, a later retirement age, or a lower income target.
- Does this account for inflation?
- No — all figures are in today's money terms, not adjusted for future inflation. For a rough real-terms estimate, consider using a more conservative expected return (e.g. your expected nominal return minus expected inflation).
- Can I use this in my own app?
- Yes — every calculator on Stupidly Clever has a matching REST API and MCP tool that runs the same underlying logic.
- What is sequence-of-returns risk?
- Sequence-of-returns risk is the danger that a market downturn early in retirement — when your pot is largest and you're drawing it down — causes permanent damage that a later recovery cannot fix. The 4% rule was designed to survive most historical sequences, but a severe early decline (like 2000–2002 or 2008) still poses meaningful risk without a spending buffer.
- How much should I save each month to reach my retirement target?
- Work backwards: decide your target pot, expected return, and years to retirement, then solve for monthly contribution. The compound interest calculator can do this in reverse — set the future value target and solve for the regular contribution.