How the Enough to Quit retirement model works

By Kenneth Bonnici, who retired at 53 · 9 min read

Published 20 July 2026

This page describes what the calculator does with your figures, so that you can see how a result is produced and reproduce or challenge it yourself. Where the model is weak, that is stated here rather than buried. It is a description of how the tool is built, not an assurance that any result is accurate or fit for your purposes: ETQ is provided without warranty of any kind, on the terms set out in the disclaimer.

The model is deterministic, and that is a deliberate choice

The model is built so that the same inputs produce the same projection. There is no randomness, no Monte Carlo simulation, no probability band, and no deliberate dependence on the time of day or the machine you run it on. Run it twice and it should return the same numbers; run it next year with the same figures and only the calendar should change.

Most serious retirement tools are stochastic: they run thousands of randomised return paths and report a success percentage. That approach answers a genuinely useful question, but a different one. It tells you how often a plan survived across simulated histories. It does not tell you what happens to your plan under a stated set of assumptions, and it makes the arithmetic almost impossible to follow by hand.

ETQ takes the opposite position. One set of assumptions, stated openly, applied consistently, with every intermediate year visible in the projection table. You can audit it. The cost of that choice is real and is set out under what the model does not do: a deterministic model cannot price sequence-of-returns risk, which is one of the most dangerous features of real retirements.

A deterministic model is not a claim that the future is predictable. It is a claim that if you are going to be wrong, you should at least be able to see exactly why.

The calculation pipeline

Every run passes through the same seven stages, in this order. The order is load-bearing: each stage depends on the one before it.

1. Activation. Decides which fields are live given everything else you have entered. If you rent, the mortgage fields are not merely hidden, they are pruned, so they cannot influence anything downstream. This is why switching a single answer can change the result more than you expect.
2. Planned sale and purchase resolution. Converts the sale and purchase years you scheduled into offsets on the projection axis, constrained to the active projection window.
3. Liquidation ordering. Fixes the order in which assets would be sold if cash ran short, either from your manual ranking or from the default rule below.
4. Validation. Checks the resolved figures for contradictions and impossible combinations. Some problems block the projection; others surface as warnings and let it run.
5. Normalisation. Converts everything to a single consistent basis, notably turning monthly figures into annual ones.
6. Timing. Anchors the projection to the current calendar year and pro-rates the first year (see below).
7. Engine. Runs the year-by-year projection. This happens twice per calculation, which is the next section.

Two scenarios, always

Every calculation runs the projection twice over the same inputs: once retiring at the statutory age you set, and once at your chosen comparison age. That is why the charts can always show a solid line against a dashed one. The two runs share every assumption, so any divergence between them is caused only by the retirement age.

How the earliest viable retirement age is found

This is the number the tool exists to produce, so it is worth being precise about it. A retirement age is treated as viable when both of these hold across the entire projection:

• Your cash balance never falls below the minimum cash reserve you set, in any year.
• Your net worth at your life-expectancy age is at least the amount you said you wanted to leave behind.

Note the first condition carefully: it is a test applied to every single year, not a check performed once at the end. A plan that runs dry at 71 and recovers by 78 is not viable, no matter how healthy the final balance looks.

To find the earliest such age, the model starts at your current age and re-runs the entire projection at each successive age, one year at a time, up to your statutory retirement age. The first age that satisfies both conditions is reported. If none does, the tool says so rather than returning an optimistic figure: it falls back to the statutory age for display and tells you no age was viable.

This is a brute-force search, not a formula. It is slower than solving analytically, and it is chosen deliberately: it means the viability test is applied to a real, full projection at every candidate age, with all your sales, purchases, crashes and events landing where you scheduled them.

First-year pro-rating

The projection starts partway through the current calendar year, not on 1 January. The first year is pro-rated by the months remaining, so income, expenses and growth in year one are scaled accordingly. Start the calculator in July and roughly half a year of each is applied; start it in December and very little is.

This is the single most common reason a result shifts slightly between one month and the next on otherwise unchanged figures.

When cash runs short: liquidation

If cash would fall below your reserve in a given year, the model stages sales of your assets to cover the shortfall. By default it sells the cheapest eligible asset first, on the reasoning that it is better to lose the smallest thing that solves the problem. You can override this ordering, and an asset ranked zero is excluded from forced sales entirely.

Sales are not free. Disposal costs are deducted from the proceeds, and selling an asset also removes whatever it was contributing: rental income stops, and its running costs stop with it. Both effects are carried through the remaining years.

Planned purchases are shielded

There is one deliberate exception. The model is written not to force-sell a property or asset to fund the deposit on a future purchase you have scheduled. If you cannot afford the purchase, the tool tells you so and asks you to reschedule or reduce it, rather than quietly selling your home to buy another one.

Your stock portfolio can fund a deposit, but only if you explicitly switch that on. It is off by default. The shielding applies to the deposit only: once you own the asset, its ongoing costs are ordinary living costs and can trigger a forced sale like anything else.

Default assumptions

These are the model's starting values. Every one of them is editable, and every one of them matters. The figures below are read from the model at page load rather than typed into this page, which is intended to stop them drifting out of step with the code.

Spending is not held flat. The default pattern applies against today's spending up to age , then to age , then thereafter, reflecting the common pattern of spending more in the early active years and less later. A steady option keeps spending flat if you prefer.

These defaults are estimates, not forecasts

They are plausible long-run figures, not predictions, and they are not tuned to any country or tax regime. The equity return in particular is a long-run nominal estimate; no such return is guaranteed over any period you will actually live through.

Their sensitivity is worth stating plainly: a one percentage-point change in the equity return or in inflation can move the earliest viable retirement age by several years. If you take one thing from this page, take that. Test your result against alternative assumptions before you act on it.

What the model does not do

This list is deliberately blunt. Every item is something a real plan may need and this tool will not give you.

• Tax, in any jurisdiction. No income tax, capital gains tax, social-security or national-insurance contributions, withholding tax or dividend tax. Enter all income and pension figures net of tax.
• Jurisdiction-specific pension rules. No state pension mechanics, defined-benefit accrual, annual or lifetime allowances, employer matching, salary sacrifice, tax-free lump sums or survivor benefits.
• Sequence-of-returns risk. Returns are applied as a steady annual rate. Real markets do not deliver an average every year, and a poor run early in retirement does lasting damage that an average rate conceals. You can schedule a crash explicitly, but the model does not test this risk for you.
• Statistical stress-testing. No Monte Carlo, no confidence intervals, no success probability.
• Healthcare and long-term care costs, beyond any figure you enter yourself.
• Currency risk on multi-currency holdings. The currency selector changes the symbol and formatting, not the exchange-rate behaviour.
• Market, property and policy forecasting. The model does not predict returns, house prices, inflation, exchange rates, taxation or legislative change.
• Personal recommendation. It does not assess your circumstances or suggest any product or course of action.

How the model is checked

Determinism is only useful if it is exercised rather than assumed, so the following checks run against the model:

• Golden snapshots. Eight fully specified household scenarios are projected and their complete year-by-year output stored. Any change to the model that moves a single figure fails the suite, so behavioural drift has to be deliberate and reviewed.
• An independent audit oracle. A second, separately written implementation of the model reconciles against the engine row by row. Two implementations agreeing is a much stronger check than one implementation agreeing with itself.
• Invariant tests covering the rules described on this page, including liquidation ordering and the purchase-funding shield.

None of this makes the assumptions correct, and none of it is a warranty that the model is free of errors. These are the checks that are run against it. They are intended to reduce the chance of a mistake passing unnoticed; they cannot eliminate it, and no claim is made that they do. ETQ is supplied as it stands, without warranties or guarantees of accuracy, completeness or reliability, and without responsibility for anything done in reliance on a result. The disclaimer governs, and prevails over anything on this page.

Your figures never leave your device

The entire calculation runs in your browser. There is no account, no signup, and the numbers you enter are never transmitted anywhere. Saved scenarios are stored in your own browser's local storage and you can clear them at any time. Full detail is in the privacy notice.

Related: the full assumptions and limitations notice, how to use the calculator section by section, and all guides.

Educational information only, not financial advice. ETQ produces illustrative model output that is sensitive to your inputs and the tool's default assumptions. Speak to a qualified professional before acting on a projection.

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