No account needed. Enter seven numbers — your current age, annual spending in retirement, current savings, monthly savings amount, expected investment growth rate, inflation rate, and safe withdrawal rate — and get an instant answer: when can you retire, and how much do you need?

Your FIRE number is the portfolio value at which your investments generate enough passive income to cover your lifestyle indefinitely at your chosen withdrawal rate. The tool applies inflation separately from your growth rate, so your results are in today's money rather than nominal future values.

Use this to get a feel for the ballpark before committing to a full profile.

The Calculator tab is your complete financial model. It separates your wealth into three pots — taxable investments, tax-free (ISA/Roth), and DC pension — and applies the correct tax treatment to each when projecting withdrawals in retirement.

Key inputs to fill in:

• Personal: current age, target retirement age, country (sets your tax regime)
• Portfolio: current balance in each pot (taxable, ISA/tax-free, DC pension), monthly contributions
• Income: expected annual retirement spending, DC and defined benefit (DB) pension details, state/social pension age and amount
• Assumptions: nominal investment growth rate (7% is a common long-run estimate for a diversified equity portfolio before inflation), inflation rate (3% default, applied separately to get real purchasing power), safe withdrawal rate (4% is the widely-cited starting point), life expectancy
• Asset allocation & retirement de-risking: optionally set a stocks/bonds split — the tool uses it to derive both your expected return and your volatility (stocks ~7.5%, bonds ~3%). In retirement the portfolio is automatically glided ~20 percentage points toward bonds (floored at 30% equity), which lowers both the expected return and the risk — reflecting how retirees typically shift to more conservative allocations. If you leave allocation off, the same de-risking is applied using the equity weight implied by your growth-rate assumption. This replaced an older flat "75% of growth in retirement" rule with an allocation-based, internally-consistent model.

FIRE type: choose Standard (full retirement), Barista FIRE (part-time work covers some expenses), or Semi-FIRE (ongoing income for a set period). Each sets a recommended withdrawal rate, which you can still override.

How part-time / barista income is treated: because it's temporary (it stops at the age you set), it's modelled where it actually changes your plan — in the Bridge analysis (you need a smaller bridge fund), the year-by-year Spending Projection, and your Monte Carlo & backtest survival — for the years you earn it. It is deliberately not subtracted from your headline FIRE Number or Adjusted Target: those are perpetual figures (spending ÷ withdrawal rate), and netting a temporary income against a forever-target would overstate it — which is why a permanent income floor (a DB or State Pension) lowers your target, but barista income does not.

Try a Scenario: the Calculator tab includes preset example profiles (e.g. UK professional, US early retiree) that pre-fill sensible defaults — a quick way to explore how the tool works before entering your own numbers.

The deterministic projection gives you a single straight-line forecast — useful as a baseline reference point, but it assumes markets grow smoothly every year, which they never do. That's what the Pro tools are for.

Your data auto-saves every few seconds. Use Save Scenario to create named snapshots — ideal for comparing "retire at 50 with lean spending" vs "retire at 55 with more comfort".

Auto-save: your current inputs are written to the cloud automatically while you're signed in — you'll never lose your work. Prefer to save manually? Turn auto-save off under Data Management → Auto-save, and use Save Now whenever you want to persist your changes.

Named scenarios: save multiple named snapshots of your inputs (e.g. "Base case", "Optimistic", "What if I stop contributing at 45"). Load any scenario from the Save/Load button to switch between them instantly.

Export to JSON: download a full backup of your inputs to your device. Useful for sharing with a financial adviser or archiving a point-in-time snapshot.

Import: restore any previously exported JSON file.

Excel export (Pro): export your full year-by-year projection data to a spreadsheet for deeper offline analysis.

Select your country in the Calculator and all projections — deterministic, Monte Carlo, and backtests — apply the key tax rules for your situation:

• 🇬🇧 United Kingdom: income tax bands, personal allowance taper (£100k–£125,140 at 60% effective marginal rate), CGT rates (post-Oct 2024: 18%/24%), SIPP 25% UFPLS tax-free element, ISA as tax-free pot
• 🇺🇸 United States: federal income tax brackets, long-term capital gains rates (0%/15%/20%), 401(k) as ordinary income, Roth as tax-free
• 🇨🇦 Canada: federal income tax, Basic Personal Amount as a non-refundable credit at the lowest rate (not a deduction), 50% capital gains inclusion rate, RRSP as ordinary income, TFSA as tax-free
• 🇦🇺 Australia: income tax, 50% CGT discount for assets held over 12 months, superannuation as tax-free after 60

How your withdrawals are taxed — the same tax model runs everywhere (the headline FIRE number, Monte Carlo, backtests and bridge analysis), so figures stay consistent across the app:

• Progressive (“smart”) tax: income is taxed through the real bracket bands for your country — including allowances and tapers — not a single flat rate.
• Withdrawal order: taxable brokerage (GIA) first, then your DC / workplace pension, then tax-free accounts (ISA / Roth / TFSA) last.
• Capital gains: only the gain portion of a taxable-account withdrawal is charged CGT — not your original capital. Set this with the “% of taxable withdrawals that are gains” control in the Calculator (default 50%); lower it if more of your pot is principal, raise it toward 100% for a worst-case view.
• Pensions: DC / workplace pension withdrawals are taxed as ordinary income (UK: 25% of each withdrawal is tax-free via UFPLS). Tax-free accounts are withdrawn at 0%.
• Tax year: bands and allowances use 2025/26 values.

These are simplified models for retirement planning purposes. Variables not modelled include Scottish income tax rates, National Insurance, dividend allowance, savings allowance, marriage allowance, High Income Child Benefit, rental income, and other personal-circumstance factors. (Pension contributions above the annual allowance are flagged with a warning, though the allowance tax charge itself isn't modelled.) Always verify with a qualified tax adviser.

Turn on “Plan as a couple” (Calculator → Assumptions → Tax Settings) to model two people as a household. Each partner is taxed under their own allowances, so the plan gets two of everything that shelters income — two Personal Allowances / standard deductions, two CGT allowances, two pension tax-free elements and two Lump Sum Allowances. This typically lowers your FIRE number and improves survival. It applies consistently across the headline number, Monte Carlo, backtests and bridge analysis.

What we assume in couple mode:

• Pooled finances: one combined investment pot and one shared household spending target — not two separate portfolios.
• Shared timeline: both partners retire together; the calculator uses one set of retirement and pension-access ages.
• Partner income: your partner’s DB / guaranteed pension and other income are taxed under their own allowances, and start at the same ages (and inflate the same way) as yours.
• Pension ownership split: the pooled pension drawdown is divided by “Your share of the pooled pension pot (%)” (you set it; default 50%). Each share is taxed under that partner’s own bands, with their own 25% UFPLS element and their own Lump Sum Allowance.
• Capital gains split 50/50: taxable-account gains are split evenly to use both partners’ CGT allowances. This is deliberately slightly conservative — a fully tax-optimal split could save marginally more.
• Freely allocable gains: we assume couples can realise gains in either partner’s name (e.g. UK inter-spouse transfers are no-gain/no-loss, or via joint accounts).
• Bridge analysis: uses one blended household tax rate per phase — exact for the income offset that determines whether each phase is funded.

Not yet modelled in couple mode: different retirement or pension-access ages per partner (a planned enhancement). State Pension is modelled — each partner gets their own. As with all tax modelling here, verify your situation with a qualified tax adviser.

Enable State Pension (Calculator → Other Income Sources) to include a government pension as guaranteed retirement income. It's off by default.

• How it's modelled: a fully-taxable income stream that starts at your chosen age (default 67) — taxed as ordinary income through your bands and Personal Allowance, exactly like a DB pension (no 25% tax-free element).
• UK amount from qualifying years: enter your National Insurance qualifying years (of 35) and the amount auto-fills from the full new State Pension (2026/27 ≈ £12,548/yr at 35 years, pro-rata below that). Check your figure on your gov.uk State Pension forecast.
• Other countries: enter your government pension (US Social Security, Canada OAS/CPP, Australia Age Pension) as an annual amount. It's modelled generically as fully-taxable income — accurate for the UK, an approximation elsewhere (e.g. US Social Security is only partly taxable).
• Couples: each partner has their own State Pension (their own qualifying years), starting at the same age.
• Where it applies: it reduces the funding gap in Monte Carlo, backtesting and the bridge analysis.

Important: the headline FIRE Number is a deliberately conservative "your portfolio funds all spending" target — it does not subtract guaranteed income. Neither State Pension nor DB pension reduce the headline FIRE Number; they only improve the Pro projections (Monte Carlo, backtests, bridge).

Real retirements aren't smooth. The Retirement Events panel (under the Calculate button) lets you add one-off events that happen during retirement and see how they change your plan's resilience:

• Money in — an inheritance, downsizing your home, or selling an asset, added to your taxable, ISA/tax-free or pension pot.
• Money out — a major purchase, a wedding, helping family, or a one-off care cost.

Enter amounts in today's money at the age they occur. They flow through your Retirement Spending Projection, Monte Carlo simulations, historical backtests and the bridge-to-pension analysis, applied year-by-year on each market path and in each bridge phase — so a one-off expense shows as a dip in your portfolio balance and a spike in that year's withdrawal, a big outflow during an early downturn is correctly punished (sequence-of-returns risk), it can shift whether a bridge phase stays funded, and money out is grossed up for tax just like any other withdrawal.

Note: like guaranteed income, retirement events refine the Pro projections — they don't change the conservative headline FIRE Number.

The Reach your goal panel (under the Calculate button) works backwards from a goal instead of forwards from your inputs. It solves three questions:

• Required monthly savings: "To retire at age X on £Y/year, how much must I save each month?"
• Sustainable income: "Saving £Z/month and retiring at age X, what yearly income could I sustain?"
• Earliest retirement age: "Saving £Z/month for £Y/year of income, what's the youngest age I could retire?"

It uses your current plan settings (savings, growth, inflation, tax wrappers, withdrawal rate) and targets the same portfolio-only FIRE number as the headline — so, like the headline, it excludes DB & State Pension (those improve the Pro projections). The "Use this in my plan" button drops the answer into your inputs and runs the full projection. If a goal can't be reached, it says so rather than returning a misleading number.

The Net Worth tab keeps the input simple — you sort your money into six everyday categories — and InflectionFI works out the FIRE-specific numbers for you. The headline is the one a generic net-worth app won't give you: how much you could actually retire on today.

• Available for early retirement (the headline): cash + ISA + taxable investments — the money you could live on now. Pensions and property are excluded because you can't spend them yet.
• Six categories: Cash & savings, Investments (ISA vs general), Pensions (DC or DB), Property (home vs rental), Other assets, and Debts. Each line is just a name, an owner and a value — add as many as you like.
• DB / final-salary pensions: enter the annual income and we capitalise it into a net-worth value at your safe-withdrawal rate (e.g. £10k/yr ÷ 4% = £250k), so guaranteed pensions show alongside your pots.
• Locked until pension age: your pension pots, with a countdown to when they unlock (set your own access age — 55, 57, or your scheme's).
• Sink fund: a place for money earmarked for a known future cost — tracked, but deliberately excluded from your net worth and the available figure.
• Your home: always counts toward total net worth, but is kept out of the "available" figure by default — one switch includes it.
• Two partners: tag each line You, Partner, or Joint (split 50/50); rows are colour-coded by owner (you in indigo, your partner in pink), and the summary shows each share and the combined total, always reconciling to the whole.
• History (Pro): "Save snapshot" records the full picture on a date, a chart tracks the trend, and below it a spreadsheet-style table lays out every value you've saved across each snapshot — with a net-worth total row.
• Import & export: export everything to a formatted Excel workbook, or import a spreadsheet and let AI sort it into categories (Ultra) — pick the right tab, review the accounts, and if your sheet tracks multiple months it imports each one as a snapshot (the latest becomes your current entries).
• Clear & privacy: Data Management → Clear Net Worth Data wipes your entries (with a confirmation, and an option to keep your saved snapshots) so you can start fresh. Every figure is stored in your own account, encrypted at rest, and included in your data export — nothing is shared.

The single most important tool for validating a retirement plan. Instead of assuming markets grow smoothly at 7% every year, Monte Carlo runs 10,000 different random market sequences using your growth and volatility assumptions, then counts how many of them result in your portfolio surviving to your life expectancy.

Why it matters: a plan that looks fine on a straight-line projection can fail 30% of the time if you retire into a bad sequence of returns. The first decade of retirement is the most dangerous — a market crash early on permanently impairs the portfolio's ability to recover.

What to aim for: 85%+ success rate is generally considered robust. Below 75% means your plan has meaningful shortfall risk and you should consider retiring later, spending less, or building a larger buffer.

Spending flexibility: if you set a flexibility % (in the Monte Carlo controls), the simulation applies a Guyton-Klinger-style guardrail — when your withdrawal rate rises more than 20% above its starting level (your portfolio has fallen behind), it trims spending, scaling up to your chosen % as the drawdown deepens, then restores it once markets recover. Willingness to cut spending in bad years is one of the most powerful ways to improve plan survival.

The simulation models withdrawals from all three pots in the correct order (taxable first, then pension, then tax-free) with estimated tax calculations at each step, based on core income tax and CGT rules for your selected country.

Monte Carlo uses synthetic random returns. Backtesting uses real historical market data — it replays your exact withdrawal plan as if you had retired at the start of each of five major crises and asks: would you have run out of money?

The five scenarios tested:

• 2008 Global Financial Crisis — S&P 500 fell ~56% peak-to-trough
• 2000–2002 Dot-com bust — tech-heavy portfolios fell ~78%
• 1973–74 Oil Crisis & 1970s stagflation — a decade of high inflation and stagnant growth
• COVID-19 crash (2020) — fast, sharp crash followed by rapid recovery
• 1987 Black Monday — the fastest single-day crash in history, followed by recovery

Surviving 2008 and the dot-com bust gives reasonable confidence. The 1973–74 stagflation scenario is the most relevant for anyone worried about inflation eroding purchasing power.

Most early retirees face a gap: they want to stop working at 45 or 50, but their pension is locked until 57 (UK minimum access age from 2028; currently 55) or 59½ (US), and their state pension doesn't arrive until 66–67 (UK, rising to 67 between 2026–2028) or 62–67 (US, depending on birth year). The bridge strategy analyses whether your non-pension assets can sustain your lifestyle across all three phases.

The three phases modelled:

• Phase 1 — Early retirement to pension access: living entirely from taxable and ISA/tax-free pots
• Phase 2 — Pension access to state pension: drawing from all pots including DC pension (25% tax-free element applied)
• Phase 3 — State pension age onwards: state/social pension supplements withdrawals, reducing portfolio drawdown

The tool tells you the exact bridge fund size required and flags if Phase 1 would exhaust your accessible assets before your pension unlocks — the most common shortfall scenario for early retirees.

Year-by-year breakdown: expand the spreadsheet under the bridge cards to see every retirement year — each income stream (DB, DC, State Pension, other, part-time), any windfall or one-off expense you've added in that year, the net withdrawal from your portfolio, and your investment and DC-pot balances as they evolve. The withdrawal and balance figures are the bridge engine's own numbers (they reconcile to the phase results above), and you can export the whole schedule to Excel.

A year-by-year breakdown of your projected cash flows in retirement — showing exactly how much you're drawing from each pot, what tax you're paying, and how your portfolio balance evolves over time.

This makes it easy to spot problems that aggregate numbers hide: for example, a plan where the taxable pot runs dry at age 62, forcing large pension withdrawals that push you into a higher tax bracket for the rest of retirement.

Use it alongside Monte Carlo — the spending view shows the expected path, while Monte Carlo quantifies the risk around that path.

Real financial plans aren't smooth. Add one-off events at specific ages to model how they shift your FIRE date:

• Buying a home (large one-off outflow)
• Inheritance or property sale (windfall inflow)
• Career break or sabbatical (reduced contributions for a period)
• Children's university costs
• Part-time or semi-retirement income (additional earnings that reduce the amount drawn from the portfolio)

Each event is incorporated into all projections — deterministic, Monte Carlo, and backtests — so you see the full downstream impact rather than just an isolated number.

Shows how your estimated marginal tax rate evolves year by year in retirement based on your withdrawal sequence, highlighting patterns in your projected tax exposure. Based on simplified models — see Tax Countries Supported for scope and exclusions.

Common patterns it surfaces:

• UK: staying below the personal allowance taper (£100k) to avoid the 60% effective marginal rate; drawing pension income below the basic rate band
• US: Roth conversion ladders in low-income years; harvesting long-term capital gains at 0% in the 10%/12% brackets
• General: sequencing withdrawals across pots to minimise total tax across a 30+ year retirement

After running any Pro calculation, Ultra subscribers can generate an AI analysis of that specific result. The AI has full context: your inputs, Monte Carlo success rate, backtest outcomes, tax profile, bridge viability, and spending trajectory.

What it provides:

• Plain-English summary of what your results actually mean
• Risk identification — the two or three factors most likely to derail your plan
• Concrete optimisations — contribution changes, withdrawal sequencing, pot allocation tweaks
• Scenario commentary — what happens if growth is 1% lower, or you retire two years earlier

The AI tab provides an open-ended chat interface where you can ask anything about your plan. All responses are generated from your actual data, not generic advice.

AI analysis is not financial advice. Always consult a qualified adviser before making major financial decisions.

Nominal growth: the default expected return is 6% per year for a diversified portfolio (before inflation). You can change this directly, or let it be derived from your stocks/bonds split.

Inflation: a default of 3% per year is applied separately from growth, so every result is shown in today's money (real purchasing power) rather than inflated future pounds/dollars. Your retirement spending target is grown by inflation up to your retirement date, then held constant in real terms.

Monthly compounding: growth is compounded monthly using the geometric rate (1 + annual)^(1/12) − 1, not the cruder annual ÷ 12 approximation — so a 6% annual assumption compounds correctly rather than slightly overstating returns.

Per-asset assumptions: when you set a stocks/bonds split, the tool derives both return and risk from it — stocks ~7.5% return / 18% volatility, bonds ~3% return / 5% volatility. If you leave allocation off, the equity weight is implied from your growth-rate assumption instead.

Retirement de-risking (glide-path): at retirement the portfolio is automatically glided ~20 percentage points from equities toward bonds (floored at 30% equity), reflecting how retirees typically shift to safer allocations. This lowers both the expected return and the volatility used in retirement.

This allocation-derived model replaced an older flat "75% of growth in retirement" haircut, which was arbitrary and not internally consistent with the volatility used.

Monte Carlo runs 10,000 simulated market paths using geometric Brownian motion (log-normal returns) — the standard model for compounding asset prices, which keeps returns realistically skewed and can never take your portfolio below zero in a single step.

Each year's return is drawn from your expected return and volatility, with the drift set as μ = log(1 + expected return) so the median path matches your assumption rather than overshooting it.

The success rate is simply the share of those 10,000 paths in which your portfolio survives to your life expectancy. Because each path is a different sequence of returns, this captures sequence-of-returns risk — the danger that an early crash does lasting damage — which a straight-line projection cannot show.

The default safe withdrawal rate is 4%, the figure popularised by the Trinity Study: a 4% initial withdrawal, increased each year with inflation, had a 95%+ success rate over 30-year US retirements (1926–1995 data).

Your FIRE number is your target real spending divided by this rate (e.g. £40,000 ÷ 4% = £1,000,000). A lower rate is more conservative and demands a larger portfolio; a higher rate is more aggressive. The 4% rule is a useful starting point — Monte Carlo and backtesting are what stress-test whether your specific plan actually holds up.

All four projection surfaces — the headline FIRE number, Monte Carlo, historical backtests and the bridge analysis — run through the same tax engine and the same three-pot withdrawal logic, so their figures stay consistent with each other rather than telling four different stories.

Why deterministic and Monte Carlo can still differ: the straight-line projection and the bridge use expected returns, while Monte Carlo uses random sequences. A gap between them isn't an inconsistency — it's exactly the sequence-of-returns risk you're trying to measure.

The calculation engines are covered by an automated test suite (math, tax, projections and Monte Carlo) that must stay green before any change ships. See Tax Countries Supported above for the full tax model and its documented exclusions.