How Much You Need to Retire — The Retirement Number Explained
What is a retirement number?
The total invested portfolio you need so that withdrawals can fund your lifestyle without running out. It depends on three inputs: annual expenses, expected returns after inflation, and how long the money must last.
The 25x rule
Example: $40,000 yearly spending → 40,000 × 25 = $1,000,000. The logic: withdrawing 4% of the portfolio in year one (1 ÷ 25 = 4%), then adjusting withdrawals for inflation, historically sustained 30-year retirements.
Step-by-step: your own number
- Estimate annual expenses in today's money — use actual spending, not income. Exclude mortgage-if-paid and commuting costs; add healthcare.
- Adjust for inflation to your retirement year: expenses × (1 + rate)^years (see the inflation guide).
- Apply the multiplier — 25x for ~30-year horizons; 30–33x (3–3.3% withdrawal) for 40+ years.
- Subtract guaranteed income — pensions or rental income covering part of expenses reduce the required portfolio proportionally.
- Check savings trajectory — run the number through the Retirement Calculator with your monthly contributions.
Worked example
Today's expenses $36,000 · retiring in 20 years · inflation 3%
Future annual expenses = 36,000 × 1.03²⁰ ≈ $65,000
Target at 25x = $1.63M · at 30x (longer horizon) = $1.95M
A $500/month SIP at 8% for 20 years builds ≈ $295k — showing why earlier, larger contributions matter.
Where the rule breaks down
- Sequence risk: a crash right after retirement damages the portfolio far more than the same crash earlier.
- Very long horizons: 45-year retirements need lower withdrawal rates.
- Healthcare shocks: late-life medical costs are the most common budget break.
- Country risk: historical US returns don't automatically transfer to other markets.
Levers that move the number most
| Lever | Effect |
|---|---|
| Cut expenses by $5,000/yr | Target drops by ~$125,000 (25x) |
| Retire 5 years later | Higher savings + fewer withdrawal years compound strongly |
| Pay off home before retiring | Removes the biggest single expense line |
Why the 4% is a starting rate, not a flat amount
The guideline comes from historical simulations of balanced portfolios surviving 30-year retirements — it is evidence-based but not a guarantee. What it actually specifies is the first-year withdrawal; after that you raise the dollar amount with inflation. On a $1,000,000 portfolio with 3% inflation, the withdrawal path looks like: Year 1 $40,000 → Year 2 $41,200 → Year 3 $42,436 → Year 4 $43,709 → Year 5 $45,020. Same 4% start, growing dollars — which is why a portfolio that only yields 4% nominal cannot sustain it, and why real (after-inflation) returns are the number that matters. The Retirement Calculator models this trajectory for your own numbers.
Worked example: Retirement Calculator at its default inputs
Open Retirement Calculator and press calculate without editing a field. What comes back is the table and result below, so the retirement numbers here are checkable in one click.
| Input | Default |
|---|---|
| Current Savings | 50000 |
| Monthly Contribution | 500 |
| Annual Return (%) | 7 |
| Years to Retirement | 30 |
| Target Amount (for solve modes) | 1000000 |
Result: Retirement Fund: $1,015,810.37
The steps behind that answer
- Solving for Final Amount
- Step 1: Monthly rate = 0.5833%
- Step 2: FV of current savings = $50000×(1+r)^360 = $405824.87
- Step 3: FV of contributions = $500×[((1+r)^360-1)/r] = $609985.50
Sensitivity: Current Savings from half to one-and-a-half times
Same calculator, same fields, one change: current savings.
| Current Savings | Result |
|---|---|
| 25,000 | Retirement Fund: $812,897.93 |
| 50,000 | Retirement Fund: $1,015,810.37 |
| 75,000 | Retirement Fund: $1,218,722.81 |
If the rows barely differ, current savings is not your lever — change a different input. If they swing widely, get that number right before trusting the total.
Related guides
The corpus is a function of three numbers
How much you save, how long it compounds, and what return it earns. Of the three, the saving rate is the one you control and the one that moves the result most in the early years; returns dominate later, when the balance is large.
A useful sanity check is the safe withdrawal rate: a corpus of roughly 25 times your annual spending supports a long retirement at about 4% a year, before fees and taxes.
Inflation turns a big number into a small one
A retirement corpus is spent over decades, so it has to be expressed in the prices of the years it will be spent. At 6% inflation, a monthly need of 100 today becomes about 320 in twenty years.
Do the planning in today's money with a real return, or in future money with a nominal return. Mixing the two is the error that makes a plan look comfortable when it is not.
Sequencing risk and the order of returns
Two portfolios with identical average returns can produce very different retirements depending on whether the bad years arrive early. Withdrawing from a falling portfolio locks in losses that later gains cannot recover.
That is the argument for a cash buffer of one to three years of spending at the start of retirement, so withdrawals do not force sales during a drawdown.
FAQ
Should I include my home in the number?
Generally no — you live in it. A paid-off home indirectly helps by lowering the expenses the portfolio must fund.
What return should I assume after retiring?
Planners commonly use 4–6% nominal on a balanced portfolio, or roughly 2–3% real after inflation. Conservative assumptions build in a safety margin.
How do taxes change the math?
Withdrawals from pre-tax accounts are taxable income. Model expenses after tax, or gross them up — the calculator's assumptions page explains which basis it uses.
Frequently asked questions
Can I use this page for "spending calculator retirement"?
Yes — this guide answers the "spending calculator retirement" question: the method is explained in the sections below and the linked calculator returns the number instantly.
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