The formula
How to calculate financial independence
Financial independence is the point where investment income covers your costs and work becomes optional. This measures how far along you are, which is more useful month to month than a distant target figure.
Count only assets that could produce income: pensions, ISAs, general investment accounts, income-producing property. The house you live in does not qualify unless you intend to sell it.
The inputs, one by one:
- Invested assets — exclude your home and anything you could not draw an income from
- Annual spending
- Withdrawal rate (%)
Results appear immediately — there is nothing to submit. Changing a field rewrites the link, so you can share the exact scenario you are looking at.
The order the fields are filled in makes no difference to the result — the calculator recomputes the whole formula from whatever is currently in every field, not step by step. That means it is safe to adjust one number, watch the result change, and adjust it back, without worrying about resetting anything first.
Why financial independence matters
FIRE stands for Financial Independence, Retire Early — reaching a portfolio large enough that investment income covers your living costs, so paid work becomes a choice rather than a necessity. It is not a specific account or product, just the point at which the figures below cross over.
Most people who look up a financial independence calculation already have a specific number in mind — a quote, an offer, a target — and want to check it rather than learn the theory behind it. This page is built for that: enter your own figures, see the result immediately, and change any field to see how the answer moves without redoing the arithmetic from scratch each time.
It is also useful as a sense check before signing anything. A quote, an offer letter or a spreadsheet from someone else can contain an error, an optimistic assumption, or simply a different convention for rounding — running the same inputs through an independent calculator is a quick way to confirm a number before relying on it.
This kind of calculation rarely stands entirely alone. A financial independence figure usually feeds into a wider decision — how it compares with a competing offer, whether it fits inside a monthly budget, what it does to a longer-term plan — and the value of having it as an exact number rather than a rough guess is that those follow-on comparisons stop being guesswork too. Once one figure in a decision is precise, it is worth making the effort to get the others precise as well, rather than mixing an exact calculation with several estimates and treating the result as equally reliable.
A calculator like this one is often bookmarked and returned to repeatedly over months rather than used once, particularly for anything tied to an ongoing plan such as a mortgage, a savings goal or an investment being tracked. Because the figures live in the web address rather than only in memory, coming back to the same page with updated numbers is quicker than starting from a blank spreadsheet each time.
Worked example
Work through the defaults on this page:
- Invested assets: 320,000
- Annual spending: 38,000
- Withdrawal rate: 4 %
That gives:
- Progress to independence: 33.68 %
- Target portfolio: 950,000
- Still to accumulate: 630,000
These figures are only the calculator's own starting values, included so the working is visible rather than hidden inside the tool above. Replace them with your own numbers and the same arithmetic applies — nothing about the method changes, only the inputs feeding it.
Reading the result
Progress accelerates in a way that feels wrong at first. Going from 0% to 25% takes far longer than 75% to 100%, because in the later stretch market growth on a large balance contributes more each year than your own savings do.
Where this goes wrong. Letting spending rise as the portfolio grows. Every extra £1,000 a year of spending adds £25,000 to the target at a 4% rate, which can push the finish line away faster than you approach it.
A useful check on any unfamiliar result is to compare it against a rough mental estimate first — round the inputs to convenient numbers and see whether the calculator's answer lands in roughly the same territory. A wildly different figure usually means one of the fields was entered in the wrong unit, most often a percentage typed as a whole number where a decimal was expected, or the reverse.
No. It means the income is no longer required. Plenty of people reaching independence keep working, change to something lower paid, or go part-time — the difference is that it becomes a choice.
Include them in the total, since they will eventually fund your spending, but plan the bridge separately. Independence at 45 with everything locked in a pension until 57 is a sequencing problem, not a wealth problem.
The headline figure is progress to independence. With 320,000 invested assets, 38,000 annual spending and 4 % withdrawal rate, that comes to 33.68 %. Change any field and the figure moves with it.
Whenever one of the underlying figures changes — a new interest rate, a different balance, an updated term — since the result only reflects what is currently in the fields. There is no need to keep a separate record of past results; the web address for a filled-in version already carries the figures used to produce it.
Not unless a tax rate or a fee is explicitly one of the inputs above. Where it is not, the figure shown is a gross calculation, and any tax due depends on your personal circumstances and current tax rules, which are worth checking separately.
The arithmetic itself is exact — the calculator applies the formula shown above precisely, with no rounding until the final figure is displayed. The uncertainty, where it exists, is entirely in the inputs: an estimated rate or an approximate balance carries that same approximation through to the result.