What Is the Rule of 25?

Most personal-finance concepts are vague. "Save more." "Invest for the long term." "Plan for retirement." The Rule of 25 is different: it gives you a single, specific number to aim for. Multiply your expected annual expenses by 25, and you have a rough estimate of the portfolio required to fund the rest of your life from investments alone.

That simplicity is why the Rule of 25 became one of the most repeated ideas in the Financial Independence and FIRE community. It turns a vague ambition — "become financially independent" — into an engineering problem you can plan against and measure progress toward.

This guide walks through the Rule of 25 from the ground up: where it comes from, why it works, how it connects to the 4% Rule, what its limits are, and how to apply it to your own plan without over-relying on it.

The Rule of 25 is a shorthand for estimating your Financial Independence (FI) Number — the size of the investment portfolio that can, in theory, cover your living expenses indefinitely.

The rule in one sentence:

Spend $30,000 a year? You need roughly $750,000 invested. Spend $60,000? Around $1,500,000. Spend $100,000? About $2,500,000. That number is your target — the portfolio that, once reached, could realistically fund your lifestyle without a paycheck.

It's not a magic figure. It's a benchmark derived from decades of retirement-withdrawal research, condensed into something you can calculate on the back of an envelope.

The Rule of 25 works because a well-diversified portfolio can generate long-term returns that, on average, exceed the amount a retiree withdraws each year. If your investments grow faster than you draw them down, the portfolio can support your lifestyle for decades — and often grow while doing so.

The specific "25×" figure comes from historical analysis of stock and bond returns in the United States, most famously the Trinity Study. Researchers found that a balanced portfolio withdrawing 4% in year one — adjusted for inflation every year after — historically survived 30-year retirements in almost every rolling period tested.

Once you know a portfolio can support a 4% withdrawal, the target portfolio size is simply the inverse: 1 ÷ 0.04 = 25. Multiply expenses by 25 and you get the portfolio required to make that withdrawal possible.

The Rule of 25 and the 4% Rule are two ways of expressing the same underlying idea.

• The 4% Rule answers: How much can I withdraw each year?
• The Rule of 25 answers: How large does my portfolio need to be?

They are mathematically linked: withdrawing 4% per year is identical to needing 25 times your annual expenses invested, because 1 ÷ 4% = 25 and 1 ÷ 25 = 4%.

Whenever you see the 4% Rule mentioned, you can translate it into the Rule of 25 in your head — and vice versa. If you'd like to test both perspectives against your own numbers, the Safe Withdrawal Rate Calculator lets you flex the withdrawal rate and see how the target portfolio changes.

To use it well, be honest about the "annual expenses" input. It should represent your realistic yearly spending in retirement — including housing, food, transport, insurance, healthcare, travel, taxes, and a buffer for irregular costs like home repairs or replacing a car.

A cleaner version of the formula

If you expect guaranteed income in retirement — Social Security, a pension, part-time work, or rental income — your portfolio only needs to cover the gap:

Applying this small adjustment often lowers the required portfolio meaningfully, especially for people planning around Social Security or a defined-benefit pension.

Here's how the Rule of 25 scales across different lifestyles. All figures assume annual expenses in today's dollars.

The pattern is linear. Every extra $1,000 of annual spending adds $25,000 to your target portfolio. That's why cutting recurring expenses is so powerful in FIRE planning — and why the Financial Independence Target Calculator lets you test different spending scenarios side by side.

• Simple. One multiplication gives you a target you can memorise and revisit anytime your expenses change.
• Empirical. It's grounded in decades of historical market data rather than opinion or forecasts.
• Universal shorthand. Almost every FIRE guide, calculator, and community uses the same 25× multiplier as a common language.
• Motivating. It transforms a vague goal into a specific number you can track progress against year by year.
• Flexible. Works equally well for Lean FIRE, traditional retirement, and Fat FIRE — the multiplier stays the same, only the inputs change.

The Rule of 25 is a starting point, not a finish line. It deliberately ignores several factors that matter in a real retirement plan.

• Assumes a 30-year horizon. Retire at 40 and you may need your portfolio to last 50+ years, where the math becomes less forgiving.
• Based on US market history. International data often supports lower safe withdrawal rates, which implies a larger multiplier.
• Ignores taxes. Withdrawals from tax- advantaged accounts may be taxable; your gross expenses should already account for that.
• Ignores fees. Even a modest 0.5% expense ratio drag reduces long-run success probabilities.
• Ignores sequence-of-returns risk. A bad market in your first few years of retirement can damage the portfolio more than the average return suggests.
• Doesn't adapt to your life. Real spending isn't flat — healthcare, children, moves, and career changes all shift the picture.

None of these break the Rule of 25 — they simply mean it should be treated as a planning anchor, not a promise.

Using take-home pay instead of expenses

The Rule of 25 is applied to what you spend, not what you earn. Using income inflates the target unless your savings rate is very low.

Forgetting inflation

Your target should be expressed in today's dollars, and you should assume expenses will grow with inflation over time. The Trinity-style math already bakes inflation into the withdrawal, but your input should reflect a realistic modern lifestyle.

Ignoring healthcare costs

Early retirees in particular often underestimate healthcare before Medicare eligibility. Add a specific line item rather than trusting a generic "misc" bucket.

Treating 25× as a hard cutoff

Reaching 25× is a meaningful milestone, but few people quit the day they hit it. Many prefer a small buffer, a cash reserve, or a year or two of part-time income before fully pulling the trigger.

Not revisiting the number

Your annual expenses evolve. Recalculate your FI Number every year or after any major life change — a move, a new child, a switch in career — so the target reflects reality.

Applying the Rule of 25 is a five-step process.

• 1. Estimate realistic annual expenses. Housing, food, transport, insurance, healthcare, taxes, travel, and a buffer for one-off costs.
• 2. Subtract guaranteed income you expect from Social Security, pensions, rental income, or part- time work.
• 3. Multiply the remainder by 25. That's your baseline FI Number.
• 4. Stress-test the number. Try 28× and 33× as more conservative alternatives, especially for long horizons.
• 5. Track your progress. Compare your current net worth to the target and revisit annually.

To make this concrete, run your numbers through the Financial Independence Target Calculator. If you're earlier in the journey, the Coast FIRE Calculator shows how much you'd need invested today to reach that FI Number without any further contributions. Track how close you are with the Net Worth Calculator and revisit the Financial Independence Target Calculator to see how each year of progress moves the target.

The Rule of 25 shines when it's used for what it is: a fast, honest, first-pass estimate. It's most useful when you:

• Want to set an initial long-term savings target without building a complex model.
• Need a quick way to compare lifestyle scenarios ("what if I spent $10k less per year?").
• Are planning a roughly 30-year retirement with a diversified stock-and-bond portfolio.
• Want a shared benchmark to discuss with a partner, a planner, or the wider FIRE community.

It's less appropriate as your only planning tool if you're retiring very early, relying heavily on non-US markets, or planning around unusually variable income. In those cases, use it as the starting number and refine with more detailed withdrawal modelling.

The Rule of 25 is the simplest, most durable heuristic in Financial Independence planning. It compresses decades of research into one line of arithmetic and gives you a concrete target to build a life around.

Use it to set your first FI Number. Then refine it with the 4% Rule, real tax modelling, and calculators that account for your specific circumstances. Simplicity is a feature — but so is knowing where the simplicity ends.

Once you have your target, the rest of the journey is consistency: save what you can, invest with discipline, and revisit the number as your life evolves.