By Toolybird Team · October 2026 · 12 min read
How to Calculate Your Retirement Number
Your retirement number is your annual retirement spending multiplied by 25. Want to spend $60,000 a year? Your number is $1.5 million. That is the 4 percent rule in one sentence, and the rest of this article shows where the math comes from, how inflation changes it, and what monthly savings actually get you there.
What is your retirement number, exactly?
Your retirement number is the portfolio size that lets you stop working and fund your lifestyle from investments indefinitely. It is not your net worth, not your home equity, and not a number anyone else can hand you. It comes from your spending, because spending is the only input that determines how much income the portfolio must produce.
The standard formula: expected annual spending in retirement, minus reliable income like Social Security and pensions, multiplied by 25. The 25 comes from the 4 percent rule (100 divided by 4), which says you can withdraw 4 percent of your portfolio in the first year of retirement, adjust that amount for inflation each year, and have a strong chance of the money lasting 30 years. A $60,000 spender with no other income needs $1.5 million. That is the whole formula. Everything below is about making the inputs honest.
Where did the 4% rule come from?
The rule traces to the 1998 Trinity study, which backtested withdrawal rates against US market history from the 1920s onward. A 4 percent initial withdrawal, inflation-adjusted annually, survived nearly every 30-year scenario for a 50/50 stock and bond portfolio, including the Great Depression and the 1970s inflation. The rule assumes a 30-year retirement, which fits someone retiring at 65. Retiring at 40 is a different problem with a longer horizon, and the honest answer is that a lower withdrawal rate, closer to 3 to 3.5 percent, is safer there.
Three caveats keep the rule honest. First, it assumes a 30-year retirement, which fits age 65 but not age 40. Second, it assumes you follow the withdrawal script mechanically, while real humans cut back in bad years, which makes outcomes better than the study suggests. Third, it is based on US historical returns, and the future may differ. My recommendation: treat 4 percent as the baseline for traditional retirement and 3 to 3.5 percent as the prudent version if you are retiring decades early. Both are planning tools, not guarantees.
How do you calculate your number step by step?
Start with spending, not income. Track what you actually spend for a few months, then adjust for retirement: subtract costs that disappear (mortgage payments that will be done, retirement savings themselves, commuting) and add costs that appear (health insurance before Medicare, travel, hobbies). Most people land somewhere near 70 to 80 percent of pre-retirement income, but your actual budget beats any rule of thumb.
Worked example. You are 35, you want to retire at 65, and you estimate you will spend $80,000 a year in today's dollars. Step one: convert to future dollars. At 2 percent inflation over 30 years, $80,000 becomes about $144,900 a year. Step two: subtract reliable income. Say Social Security covers $28,000 a year in future dollars, leaving $116,900 for the portfolio. Step three: multiply by 25. Your number is about $2.92 million in future dollars. It sounds enormous until you run the savings math below, because 30 years of compounding does shocking amounts of work.
What monthly savings actually reach the number?
Here is where the number stops being scary. Investing $500 a month for 30 years at a 7 percent average annual return grows to roughly $610,000. At $1,000 a month, about $1.22 million. At $1,500 a month, about $1.83 million. These are not cherry-picked returns: 7 percent is a commonly used planning assumption for a stock-heavy portfolio after inflation.
The shape of the growth matters more than the final figure. After 10 years of $500 monthly contributions, you have roughly $86,500, and most of it is your own money. After 20 years, about $260,000, and growth is pulling its weight. After 30 years, $610,000, and compound growth did the majority of the work. Every year you delay costs you twice: one fewer year of contributions and one fewer year of compounding on everything. If you are starting late, the honest levers are saving more, retiring a few years later, or trimming the spending target, since each $1,000 of annual spending you cut removes $25,000 from the target.
Should Social Security and pensions reduce your number?
Absolutely, and this is where many people overestimate their target by hundreds of thousands of dollars. The times-25 multiplier applies only to the gap your portfolio must fill. Want $60,000 a year, with $25,000 coming from Social Security? The portfolio covers $35,000, and your number is $875,000, not $1.5 million.
Get your real Social Security estimate from the Social Security Administration rather than guessing, and use a conservative figure since the program faces long-term funding adjustments. Pensions, rental income, and realistic part-time income count the same way. One caution: do not count income you merely hope for. A side business that does not exist yet is not a pension. Count what is contracted or highly predictable, and let everything else be a bonus that makes retirement more comfortable than planned.
What changes if you want to retire early?
Early retirement breaks the 30-year assumption behind the 4 percent rule. Retiring at 45 means the portfolio might need to last 45 years, through more market cycles and more inflation. That is why the FIRE community generally plans around 3 to 3.5 percent withdrawals instead of 4 percent, which pushes the multiplier from 25 to roughly 28 to 33. A $50,000 spender needs $1.25 million at 4 percent but more like $1.5 to $1.65 million for a 50-year horizon.
Early retirees also lose two supports traditional retirees count on: Social Security is decades away, and health insurance must be bought privately until Medicare at 65, which can add $10,000 or more a year to spending. Run both scenarios in our FIRE Calculator: the standard retirement number and the early-retirement number, and compare the monthly savings each demands. The gap between them is the true price of retiring early, and it is bigger than most people guess.
How do you stay on track once you have the number?
A number you never revisit is decoration. Once a year, spend ten minutes on three updates: current portfolio value, current annual spending estimate, and years left until retirement. Plug them into our Retirement Savings Calculator and check whether you are still on pace. If a market drop knocked you 20 percent off course, do not panic and do not ignore it: small corrections now (a slightly higher savings rate, one more working year) beat big corrections later.
Automate everything you can. Contributions that leave your paycheck before you see the money happen every month without willpower. Increases tied to raises capture lifestyle inflation before it becomes spending. And keep an emergency fund separate from the retirement portfolio, because raiding retirement savings for a car repair is how good plans quietly die. The number is a compass. The monthly automation is the engine.
Examples use a 7 percent average annual return and 2 percent inflation for illustration. Estimates for planning only, not financial advice.
Frequently Asked Questions
What is a retirement number?
Your retirement number is the total savings target that lets you stop working and live off your investments. The standard way to compute it is to take the annual spending you want in retirement and multiply by 25, which comes from the 4 percent rule: withdrawing 4 percent of the portfolio in year one and adjusting for inflation afterward. If you want to spend $60,000 a year, your number is $1.5 million. It is a planning target, not a magic threshold, but having one turns the vague goal of saving for retirement into a concrete monthly savings figure you can actually act on.
What is the 4% rule and where did it come from?
The 4 percent rule comes from the 1998 Trinity study, which tested withdrawal rates against decades of US stock and bond market history. It found that a retiree with a roughly 50/50 mix of stocks and bonds could withdraw 4 percent of the starting portfolio in year one, raise that amount with inflation each year, and have the money last 30 years in nearly every historical scenario tested, including the Great Depression and the 1970s inflation. The rule assumes a 30-year retirement, which fits someone retiring at 65. Retiring at 40 is a different problem with a longer horizon, and the honest answer is that a lower withdrawal rate, closer to 3 to 3.5 percent, is safer there.
Does the 4% rule still work in 2026?
As a planning guideline, yes, with eyes open. The rule survived every historical stress test thrown at it, but critics note that future bond returns may be lower than the historical periods the study covered, and that retirees rarely follow the rigid inflation-adjusted script anyway. Real retirees cut spending in down years, earn some income, and delay big purchases, all of which make the plan safer than the paper math. My take: use 4 percent as your baseline target, treat 3.5 percent as the conservative version for early retirement, and revisit the number every few years as your spending and portfolio change.
How do I adjust my retirement number for inflation?
The times-25 math only works if the spending figure is in future dollars, the dollars you will actually spend when you retire. If you plan to spend $80,000 a year in today's dollars and retirement is 20 years away, assume 2 percent annual inflation: $80,000 times 1.02 to the 20th power is about $118,900 a year of future spending. Multiply that by 25 and your number is roughly $2.97 million in future dollars. Always compare future dollars to future dollars and today's dollars to today's dollars, or the math will mislead you. Alternatively, do the whole calculation in today's dollars and track your progress the same way.
How much should I save each month to hit my number?
Time does most of the work through compounding. Investing $500 a month for 30 years at a 7 percent average annual return grows to roughly $610,000. Double it to $1,000 a month and you land near $1.22 million. The uncomfortable truth is that the first decade feels painfully slow: after 10 years of $500 monthly contributions at 7 percent, you have about $86,500, and only a third of that is growth. By year 30, growth has done most of the lifting. That is why starting early beats saving more later, and why our Retirement Savings Calculator is worth running with your own numbers instead of mine.
Should I subtract Social Security from my retirement number?
Yes, and it changes the number more than most people expect. The times-25 rule applies to the spending your portfolio must cover, not your total spending. If you want $60,000 a year and Social Security will provide $25,000, your portfolio only needs to produce $35,000, so your number drops from $1.5 million to $875,000. Check your estimated benefit on the Social Security Administration's website and use a conservative figure, since benefits could be adjusted in the future. Pensions, rental income, and part-time work reduce the number the same way: every reliable dollar of annual income cuts the target by $25.
What is a FIRE number and how is it different?
A FIRE number (Financial Independence, Retire Early) uses the same times-25 math but applies it to a much earlier retirement, which changes the assumptions. Retiring at 40 means the portfolio must last 50 years instead of 30, so the standard 4 percent rule is shakier and many early retirees plan around 3 to 3.5 percent instead, meaning a multiplier of roughly 28 to 33 instead of 25. Early retirees also cannot count on Social Security for decades and must fund health insurance themselves before Medicare. Run both versions in our FIRE Calculator: your age-65 number and your early-retirement number, and see how different the monthly savings requirement is.
What if I am starting late? Is the number still reachable?
Starting at 50 with nothing saved, $1,500 a month for 15 years at 7 percent grows to roughly $473,000, well short of a $1.5 million target. That is the bad news, and I will not sugarcoat it. The good news is that late starters have the biggest levers: catch-up contributions let workers 50 and older put extra thousands into 401(k)s and IRAs each year, delaying retirement by even three years both adds contributions and shrinks the years the portfolio must fund, and trimming the spending target has a 25-to-1 payoff. Cutting planned spending from $60,000 to $50,000 a year lowers the target by $250,000 instantly.
Do taxes change my retirement number?
They change which number you are actually computing, so be precise about it. If your $60,000 spending target is after-tax spending and your withdrawals come from a traditional 401(k) taxed as ordinary income, you need to withdraw more than $60,000 to net $60,000, which raises the real target. Roth withdrawals and return-of-principal are not taxed, so a portfolio split across account types can lower the effective target. The clean approach: estimate your retirement tax bill first, add it to your spending target, and then multiply by 25. It is an extra step, but it keeps the number honest.
How often should I recalculate my retirement number?
Recalculate whenever something material changes and do a light review once a year. Material changes include a raise or job loss, a new child, buying a home, a health diagnosis that changes your plans, or a market swing that moves your portfolio more than about 20 percent. The annual review takes ten minutes: update your current savings, update your spending estimate, and check whether you are still on pace. The number is a compass, not a contract. People who never recalculate either undershoot and panic at 60 or overshoot and work years longer than they needed to.