How Much Do I Need to Retire?

The question behind the question

"How much do I need to retire?" sounds like it needs a financial advisor and a crystal ball. It doesn't. The number starts from one thing you already half-know: how much you spend in a year. Everything else is arithmetic built on top of that.

I find this genuinely reassuring, because it means the target isn't arbitrary — it's tied to your actual life. Let me walk through how to turn your spending into a retirement number, and then how regular investing gets you there. This is a planning framework, not investment advice, and the rules below are rules of thumb, not guarantees.

Start with your annual spending, not your income

The mistake most people make is anchoring on income. What you earn doesn't fund your retirement — what you spend does. So the first figure to nail down is your expected annual spending in retirement.

For many people that's a bit less than today's spending: the mortgage may be gone, the kids independent, the commute over. For others it's similar or higher if they plan to travel. A reasonable starting point is your current annual spending, adjusted for any obvious changes. Call this number A.

The 25x rule: your target corpus

Here's the famous shortcut. To retire, you roughly need a corpus (invested pot) of:

Target corpus = Annual spending × 25

So if you spend 20,000 units a year, your target is 500,000 units. If you spend 40,000, it's 1,000,000. Multiply your number by 25 and you have a target to aim at.

Where does 25 come from? It's the flip side of the 4% rule, which says you can withdraw about 4% of your starting corpus in year one, then adjust that amount for inflation each year, and historically the pot has lasted roughly 30 years. Since 1 ÷ 0.04 = 25, "withdraw 4%" and "save 25×" are the same idea wearing two hats.

Important caveats on the 4% rule

The 4% rule is a brilliant starting estimate, not a law. A few honest caveats I always mention:

• It assumes a long but finite retirement (around 30 years). Retire very early and you may want a more cautious 3% to 3.5% — i.e. a bigger 28x–33x multiple.
• It assumes a sensibly diversified, growth-oriented portfolio. Park everything in cash and the math doesn't hold.
• It ignores other income. Any pension, state benefit, or part-time income reduces how much your corpus has to cover, shrinking your target.
• Inflation matters. The withdrawals rise with prices, which is exactly why the corpus needs to keep growing, not just sit still.

Treat 25x as the headline and adjust the multiple up if you're retiring early or want extra safety. The retirement calculator lets you test different spending and return assumptions, and if early retirement is the goal, the FIRE calculator is built around exactly this 25x logic.

Getting there: corpus plus contributions

Knowing the target is half the job. The other half is the path. Two forces fill the gap between today and your number: the money you contribute and the growth that compounds on what you've already invested.

Suppose your target is 500,000 and you're starting near zero with 30 years to go. Assuming a long-run 8% annual return, you'd need to invest very roughly 300 units a month. Compounding does the rest — across 30 years you'd personally contribute on the order of 108,000, and growth supplies the remaining ~390,000.

Now watch what time does. Cut the runway to 20 years and the required monthly amount jumps to roughly 850 — nearly triple — for the same target, because there are fewer years for compounding to help. This is the single best reason to start early: every year you delay, the monthly cost of the same goal climbs steeply. My guide on starting small is built around exactly this idea, and you can size your own monthly number with the SIP calculator.

A simple step-by-step

1. Estimate annual retirement spending (A). Start from today's spending, adjust for known changes.
2. Multiply by 25 for your baseline target corpus (use 28–33× if retiring early).
3. Subtract other income. Pensions or benefits lower the corpus you must self-fund.
4. Work out the monthly investment that reaches the target over your timeline.
5. Revisit yearly. Spending changes, returns vary, life happens — recheck and adjust.

Takeaways

• Your retirement number starts from annual spending, not income.
• The 25x rule (the 4% rule's twin) turns spending into a corpus target fast.
• Use a larger multiple for early retirement or extra caution.
• Starting early slashes the monthly amount needed — delay is the expensive choice.

This is an educational framework, not investment advice — the 4% rule is a historical rule of thumb, real returns and inflation vary, and your plan should reflect your own circumstances.