How retirement age is calculated: the survival test

The calculator finds your earliest retirement age by running a survival test: if you stopped working at age R, would your pots fund your spending every year until age 100 without running out? It simulates year by year from R to 100. Before your pension access age, spending comes out of your ISA/GIA only: the bridge. From pension age, the drawdown strategy you pick decides which pot pays. By default both pots are drawn in proportion to their balances, so they run down together; you can instead draw the pension first or the ISA first. Once your State Pension starts, it reduces how much has to come from your own pots. The test is run on 1,000 simulated markets. The headline is the earliest age at which 80% of them (or the 70% or 90% you choose) last to 100. Next to it is the age that works if your average return arrives every year: on its own that is close to a coin flip, which is why it isn't the headline. Tax on pension withdrawals: each withdrawal is treated as an uncrystallised funds pension lump sum (UFPLS). 25% is tax free and the rest is taxed as income, stepping through the real bands on top of your State Pension, which uses your personal allowance first. So if you need £30,000 a year from your pension alone in 2026/27, the calculator draws about £32,336 gross, not the £37,500 a flat 20%-on-everything model would demand. ISA withdrawals are tax-free. Limits that shrink over time: the model works in today's money, so it also applies the UK limits that are fixed in cash and lose value to inflation. Income tax thresholds are frozen until April 2031 and then assumed to rise with inflation. Tax-free cash is capped by the £268,275 lump sum allowance, which is never indexed: at 2.5% inflation it is worth about £164,000 in today's money in 20 years, so it can limit the tax-free part of pots well below £1m. Once that allowance is used, withdrawals are fully taxable. Simplifications: GIA dividends and gains are treated as tax-free (with the £3,000 CGT exemption and £500 dividend allowance, a small GIA is close to that; a large one is not). The State Pension is held level in today's money, which is cautious, since the triple lock usually raises it faster than prices. In a year split by a milestone (pension age, State Pension age, a pot emptying), each part is taxed as if its rate of income ran all year, which is slightly cautious. This calculator does not use the 4% rule or a fixed safe withdrawal rate. Instead, it tests whether your pots survive to age 100 under a full drawdown simulation.

The pension bridge: why your ISA balance matters as much as your SIPP

In the UK your pension (SIPP or workplace scheme) is locked until age 55, rising to 57 on 6 April 2028. If you want to retire at 50 with a pension age of 57, you need 7 years of spending in accessible savings (ISA or GIA) before you can touch the pension. The survival test runs both phases in one simulation. During the bridge only your accessible pot can pay, and the plan fails the moment it runs dry, however large your pension is. After pension age, both pots (and later the State Pension) share the load. Tip: if the bridge is what holds you back (your total wealth is enough but your ISA runs dry before pension age), shifting some of your annual contributions from pension to ISA can bring your retirement date forward, even though you give up some tax relief. The workings table shows the year the ISA empties.

Why the answer is a chance, not a single number

Markets don't return the same amount every year, and the order the good and bad years come in matters as much as the average. The calculator runs 1,000 simulations, each with its own sequence of yearly returns drawn from your growth rate and volatility. Returns are lognormal and calibrated so the typical (median) year matches your stated growth. For each simulated market it finds the earliest age at which retiring would last to 100. The share of markets where retiring at age R works is your chance of the money lasting at R: the panel shows it for your target age and lists the ages that give a 50%, 70%, 80% and 90% chance. How bad is the bad case? A chance on its own hides how badly the unlucky markets end, so the panel also shows what happens in the worst 1 in 10 markets if you retire at the headline age: the age the money runs out, or what is left at 100. The simulated markets are seeded from your inputs, so the same scenario and the same share link always give the same answer. Being flexible helps: the model spends the same amount every year whatever markets do. Research on UK retirees (Morningstar, 2026) finds that being willing to cut spending after a bad year lets you safely spend noticeably more, so treat the headline as a cautious plan.

Crash tests: sequence-of-returns risk

The Monte Carlo run shows a statistical range; stress tests force a specific bad scenario, to answer "What if the market crashes the year I retire?" The 30% fall applies a −30% real return in your first full year of retirement; the 10 flat years apply a 0% real return for your first 10 full years of retirement. The scenario is applied to the average-market path, to every simulated market and to the range chart, and the retirement ages move later until the plan survives it.

Real terms vs nominal: why the chart figures don't "grow" with inflation

Everything runs in today's money (real terms). If you enter a 7% expected return and 2.5% inflation, the model uses a real return of ≈4.4%: the purchasing power gain after inflation. Your spending target stays constant on the chart because both the pots and the withdrawals are expressed in today's pounds. A nominal model would show numbers growing to impressive-looking sums by age 70, but that growth is mostly just inflation. Real terms strips it out so the chart is honest about what your money will actually buy. Contributions are assumed to keep pace with inflation. Limits fixed in cash, such as the frozen income tax thresholds and the lump sum allowance, are converted into today's money for each future year, so they shrink in the chart's terms just as they will in reality. Fees come off growth before inflation: 7% growth with 0.3% fees and 2.5% inflation is a real return of about 4.1%.

Can I change the tax rules the calculator uses?

Yes. Open Fine-tune assumptions, then Tax & pension rules. Every figure starts at today's UK value and can be changed: the personal allowance and its taper, each income tax band and rate (for the rest of the UK and for Scotland), how long thresholds stay frozen and what happens after, the tax-free share of pension withdrawals and its lifetime cap, the saving cap once you draw a pension, State Pension growth above prices, and the age your money should last to. Changed figures are marked, carried in your share link, and the result says it is using your own rules. Reset to current UK rules puts everything back.

UK FIRE Calculator | When Can You Retire Early?

About you

Current age

Yearly spending once retired

from retirement

In today's money, after tax: what your life would cost if you retired today. Prices are taken care of, so don't add inflation yourself. Use a spending change for later years, such as spending less after 75.

What you have, and save each year

ISA & savings today

Money you can spend at any age: ISAs, general investment accounts and cash. It pays for the years before your pension unlocks.

Pensions today

All SIPP and workplace pension pots. Locked until your pension access age.

Into ISA & savings each year

In today's money; assumed to rise with prices until you retire.

Into pensions each year

The total reaching the pot: yours plus tax relief plus your employer's. Paying in £6,400 from take-home pay becomes £8,000 with basic-rate relief.

Fine-tune assumptions Growth, fees, pensions and tax. The defaults suit most people.

Markets · figures are in today's money

Long-run growth per year

The compound yearly growth you expect before inflation and fees: global shares ≈ 7–9%, a balanced fund ≈ 5–7%.

Fees per year

Fund plus platform charges, taken off growth. See what they cost you with the fee drag calculator.

Inflation

Used to turn growth into growth above prices, and to shrink the tax limits that are frozen in cash.

Ups and downs (volatility)

How much returns swing from year to year (standard deviation): global shares ≈ 15–17%, a 60/40 mix ≈ 10–11%, bonds ≈ 5–8%. Higher means a wider range of outcomes.

Pensions

Pension access age

Rises from 55 to 57 on 6 April 2028. Born between April 1971 and April 1973? You keep 55 only if you start taking benefits before then, or have a protected age. Set from your age; you can change it.

Include the State Pension

State Pension per year

The full new State Pension is £12,548 (2026/27). Check your forecast.

State Pension starts at age

Rising from 66 to 67 by 2028, then 68 for those born after 5 April 1977.

Tax on pension income

How to work out the tax

25% of each pension withdrawal is tax-free, and the State Pension uses your personal allowance first. ISA withdrawals are always tax-free.

Where do you pay income tax?

Scotland has six bands on pension income, from a 19% starter rate to a 48% top rate.

After you stop full-time work

Stop saving once retired Untick if you will keep paying in for a while, for example from part-time work.

Tax & pension rules Today's UK figures (2026/27). Change any of them to test a different future.

Income tax

Personal allowance

Allowance starts shrinking above

Allowance lost per £1 above that

Bands: England, Wales & NI

Bands: Scotland

Each band is written as on GOV.UK: the rate applies to income up to the amount shown, for someone with the full allowance.

How the limits change

Thresholds frozen until April

After that

A frozen threshold shrinks in today's money every year, so more of your income is taxed.

Pensions

Tax-free part of each withdrawal

Lifetime cap on tax-free cash

Cap rises with prices (today it is fixed)

Saving cap once you draw a pension

State Pension growth above prices

0% keeps it level in today's money. The triple lock has raised it faster than prices, so 0.5% to 1% is a less cautious choice.

Allowances and plan length

ISA allowance

Pension annual allowance

Money should last to age

The two allowances only trigger warnings above; they don't change the figures.

You could retire at

with an chance your money lasts to 100

If markets match your assumption - -

In a bad market (worst 1 in 10) - -

Left at 100 in an average market - in today's money

Your pots when you retire at -

ISA & savings -

Pensions -

Total -

Your target retirement age

Chance your money lasts if you retire at 55 -

Adjust the inputs to see your result.

Your savings and pensions, year by year

Average market

ISA & savings Pensions

Try something different

Retirement age

Drag to see another age -

Crash test

A bad start to retirement

Which pot to spend first

Once your pension unlocks

This path assumes you retire at age -.

Year-by-year workings

Average market

Every year of the path above, in today's money. Spending is met from ISA withdrawals plus pension withdrawals and the State Pension after tax. Pension withdrawals are shown before tax; the tax-free cash is part of them.

Age	Spending	ISA in	Pension in	ISA out	Pension out	State Pension	Income tax	Tax-free cash	ISA balance	Pension balance	Notes

Range of outcomes

Simulations

Total wealth by age when everyone retires at the age shown, across all the simulated markets.

Middle half of markets 8 in 10 markets Typical market

Show:

Illustration only, not financial advice. Based on 1,000 simulated markets, all in today's money. Markets are uncertain and past performance is no guarantee of future returns.

How the calculator works

The maths behind your retirement age, and what to do if you want to change it.

Know your real assets, not a guess.

This model is only as good as the growth rate and expenses you type in. Omnicogi replaces the guesswork: it pulls your actual ISA, SIPP and GIA balances from your broker CSVs and calculates your real XIRR, so you always know how your numbers compare to the plan.

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