Enter your current net worth, monthly savings, expected return, and annual expenses to find your financial-independence date — and whether you are already Coast FI against UK state pension age 68.
A UK-localised calculator pre-filled in GBP. Use it to project growth inside a Stocks & Shares ISA, LISA, or SIPP — all of which compound tax-free up to annual allowances.
FIRE rests on one formula: FI target = annual expenses ÷ safe withdrawal rate. At 4% SWR that is 25× your expenses. Once your portfolio hits that number it can theoretically sustain inflation-adjusted withdrawals indefinitely.
In a UK context: your ISA is the primary FIRE vehicle — growth and withdrawals are entirely tax-free at any age, so the nominal rate this calculator shows is also your real take-home. A SIPP adds income-tax relief on contributions (making it extremely efficient) but is only accessible from age 57, rising to 58 in 2028. Most UK FIRE practitioners bridge the gap to 57 with their ISA and LISA, then draw from the SIPP thereafter.
The UK state pension age is currently 68. If your projected FIRE date is before 68, you will need to fully self-fund the gap — but if you are already Coast FI (shown above if applicable), your current portfolio can do it without further contributions.
Worked example: A £10,000 ISA balance plus £500/month at 7% for 25 years compounds to roughly £415,000 — entirely tax-free because ISA growth escapes capital gains and dividend tax.
FIRE stands for Financial Independence, Retire Early. The target portfolio is typically 25× your annual expenses, derived from the 4% safe withdrawal rate (Trinity Study). Many UK FIRE seekers hold their portfolio across an ISA (tax-free drawdown at any age) and a SIPP (accessible from age 57).
The SWR is the annual percentage you can withdraw without running out of money. The Trinity Study found 4% survived 30+ years in 95% of scenarios. For UK early retirees with 40+ year horizons, 3–3.5% is often preferred to give more margin against a prolonged bear market early in retirement.
For a globally-diversified equity index fund inside a Stocks & Shares ISA or SIPP, 6–8% nominal is a common historical assumption. Growth inside both wrappers is tax-free, so the nominal rate is also your effective rate. Outside a wrapper, model 1–2% lower due to capital gains tax (10–20%) and dividend tax (8.75% / 33.75% depending on band).
Coast FIRE: your portfolio is large enough that, left untouched, it will grow to your FI target by UK state pension age (68) — so you can stop contributing now. Lean FIRE: retiring under roughly £20,000/year. Fat FIRE: retiring on £60,000+/year. Just change the annual expenses input to model each scenario.
Inside an ISA or LISA, growth and withdrawals are tax-free at any age. A SIPP offers income-tax relief on contributions but is only accessible from age 57 (rising to 58 in 2028). Most UK FIRE practitioners bridge the gap with their ISA. The UK state pension becomes payable at age 68 — if your projected FIRE date is before that, plan to fully self-fund the gap.
ProFinanceCast turns one-off calculations into a living 10-year forecast that updates as your income, expenses, and goals change. Free forever for the core forecast.