How to Calculate Your Retirement Number (Without Overcomplicating It)

Key Takeaways:

• Start with what you’ll spend. Pin down a normal year of retirement costs: the everyday bills plus the big items that only land every few years. Everything else you calculate rests on that number.
• Subtract the income you can count on, and note when it starts. Social Security, a pension, and other steady checks shrink what your portfolio has to cover, but only in the years they’re paying out.
• Turn the leftover gap into a target. Take the yearly amount your investments have to produce and divide it by a withdrawal rate that fits your timeline. That’s your number, and it’s a starting point rather than a fixed answer.

Calculating your retirement number sounds like a simple exercise, right up until you open three online calculators, get three different answers, and start to scratch your head.

Those calculators disagree because they’re all guessing at your life. You’re not. When you build the number from a few pieces you know, and hold onto it loosely, you end up with something far more useful than a generic estimate. Nobody has a crystal ball for the next 30 years, and you don’t need one to get started.

Estimate What You’ll Spend in Retirement

Your salary tells you almost nothing here. Two people earning the same paycheck can need very different amounts saved, depending on their debt, their lifestyle, and the bills that follow them into retirement.

So picture a realistic retirement year, one where some costs vanish, some stick around, and a few climb. Aim for a normal year, and leave yourself room for the expensive things that only show up once in a while.

Sort Your Spending Into Three Buckets

You don’t need to track every coffee. Three buckets give you enough detail to work with, without turning this into a second job.

Here’s the framework:

The must-pays. Housing, utilities, groceries, transportation, insurance, routine healthcare, and everything else it takes to keep the lights on each month.

The nice-to-haves. Travel, dining out, hobbies, gifts, the fun stuff. They fund the retirement you want, and you can dial them back if a year goes sideways.

The every-so-often big ones. A new roof, a replacement car, a major dental bill, helping a kid. The purchases that skip your monthly budget and then blindside it.

Adjust Your Current Spending for Retirement

Your spending today is a solid starting point. Just don’t copy it straight across, because a lot changes the day the paychecks stop.

First, strip out the costs of working and saving. Retirement contributions, the commute, work clothes, payroll taxes. All of that can disappear with your last paycheck, and none of it needs replacing.

Housing and lifestyle need a harder look. Maybe the mortgage is gone, maybe you move, or maybe the loan is paid off, but the property taxes and upkeep climb anyway. In a high-cost market, a paid-off house can still cost more to hold than people expect, which is one reason the number looks different in San Diego than it does elsewhere. And travel, hobbies, and home projects tend to grow once your weekdays open up.

Healthcare is the wild card, especially if you retire before 65. Medicare generally starts at 65, though some people qualify sooner, so you may have years to cover on your own first.¹ If you’ve got a health savings account (HSA), those dollars can help with qualified medical costs.

One more call: decide whether your spending figure is before-tax or after-tax, then stick with it. Lean toward before-tax. Withdrawal rates are normally applied to a pre-tax balance and gross withdrawals, so running the whole exercise in after-tax dollars will understate the portfolio you need whenever the money sits in a traditional IRA or 401(k). If you’d rather think in after-tax terms, gross your spending up for the taxes your withdrawals will trigger before you divide. Our tax planning work often starts right here.

And base the figure on a typical year rather than an unusually cheap or expensive one.

Figure Out How Much Your Portfolio Has to Cover

Your portfolio usually doesn’t fund the whole thing. Steady income from elsewhere picks up part of the tab, which means less has to come out of your investments, and less has to be sitting in them to begin with.

For Social Security, don’t just grab the first number on your statement. Use an estimate tied to when each spouse plans to claim, since waiting bumps the monthly check up, all the way to age 70.²

For a pension, use the payout option you’ll probably pick, survivor coverage and all, and note whether it keeps pace with inflation. A lifetime annuity counts too, as long as it pays for life. Don’t confuse that with a payment that’s only handing back your own principal for a while.

Rental income, a business, royalties, and part-time work can all count as well, as long as the net income looks steady enough to lean on. But watch the timing. If Social Security or a pension doesn’t kick in until a few years into retirement, cover those early years on their own, since that money isn’t there yet.

One thing you don’t subtract: the dividends, interest, and distributions your portfolio itself throws off. Those are already built into your withdrawal rate, so counting them separately would credit the same dollars twice.

Turn the Yearly Gap Into a Portfolio Target

Your yearly gap is simple: what you’ll spend minus the dependable income you’ll have that same year. That gap is the piece your investments have to cover.

Divide it by a withdrawal rate, and you’ve got your starting target. It’s a planning figure that will move as markets, taxes, and your spending shift over time.

Pick a Withdrawal Rate That Fits Your Plan

Your withdrawal rate is the slice of your portfolio you plan to spend in year one, before any later adjustments. People mix it up with the investment return, but the two are different things: the return is how fast the money grows, while the withdrawal rate is how much you pull out.

Rates in the 3% to 4% range come from research on how long a diversified portfolio has historically supported inflation-adjusted withdrawals over a multi-decade retirement.³ They are assumptions, not guarantees, and they depend on how the portfolio is built.

Here’s the trade-off: a lower rate means a bigger target but more safety margin, while a higher rate shrinks the target and leaves you less cushion for a rough early market, a surprise expense, or a retirement that runs 35 years instead of 25.

Your asset mix, your outside income, how flexible your spending is, and how much the portfolio has to carry all push that rate around. Early losses tend to sting more when you’re pulling money out at the same time, so a long horizon or a meaningful legacy goal usually argues for a more conservative assumption. That connection between the rate you can support and the way the money is invested is the part most calculators skip.

Do the Math

Once your spending, your income, and your rate all cover the same year, the arithmetic is easy. Keep the annual numbers annual, and write the rate as a decimal.

Two quick formulas:

• Yearly spending − dependable yearly income = yearly portfolio gap
• Yearly portfolio gap ÷ withdrawal rate = your retirement number

If some income starts later, you’ll run it twice: once for the bridge years, once for after the benefits show up. What you land on is the investable pile you need at the start. How you arrange and invest the accounts is a separate conversation.

Here’s what that looks like. Say you expect to spend $84,000 in a typical retirement year. You’ve got $36,000 coming from Social Security and $12,000 from a pension. Your portfolio covers the rest.

• Yearly spending: $84,000
• Dependable income: $36,000 + $12,000 = $48,000
• Yearly portfolio gap: $84,000 − $48,000 = $36,000
• Withdrawal rate: 4.0%
• Retirement number: $36,000 ÷ 0.04 = $900,000

Now divide that same $36,000 gap by 3.5% instead, and the target jumps to about $1.03 million, even though your spending didn’t budge. The more conservative rate simply calls for a larger portfolio to support it.

And if Social Security doesn’t start for three years, you cover those bridge years without it, then settle into the $900,000 figure once both checks are flowing.

This example is hypothetical and provided for illustration only. The withdrawal rate is an assumption rather than a guarantee. The figures don’t reflect the experience of any Bull Oak client or any particular investment result, and your own outcome will differ.

Sanity-Check the Number

First, make sure every figure is in the same dollars. Today’s money or future money, either one works, but your inflation assumptions have to match across spending, income, and assets. Mix them and the result will be misleading.

Then stack the number against what you’ve saved for it: workplace plans, your individual retirement accounts (IRAs), brokerage accounts, HSA dollars, and cash you’ve set aside. Leave your house and belongings out, unless you plan to sell, downsize, or borrow against them.

Account type matters as much as the balance. A pre-tax IRA hands you taxable income on the way out, while qualified Roth withdrawals generally come out tax-free.⁴ That means your balances can look sufficient on paper while producing very different amounts of spendable income, especially once required minimum distributions (RMDs) begin.

From there, treat the result as a range you can flex. Run a baseline and a more conservative version, then measure any shortfall against the years you’ve got left, what you’re saving each month, and a realistic return. Compounding can do a lot of work over time, provided your growth assumption fits how the portfolio is invested.

And remember you’ve got levers. Working a couple more years, trimming the flexible spending, or lining up more guaranteed income can all shrink what you still need to save. Revisit the math when something meaningful changes: a raise, a move, a new benefit estimate. Ordinary market swings alone aren’t a reason to rebuild the plan.

Calculating Your Retirement Number FAQs

1. What does a retirement number actually represent?

It’s the investable pile you’d need to cover the gap between what you’ll spend and the income you can count on. Because it rests on assumptions about taxes, inflation, returns, and how long you’ll live, it works best as a planning range.

2. How accurate does my spending estimate need to be?

Close enough to capture a normal year, with your must-pays, your fun money, and the occasional big expense. A workable figure you revisit beats a perfect budget you build once and forget.

3. How do I handle income that starts after I retire?

Treat the early years as their own bridge and cover them separately. Then model the later phase using what you expect Social Security or a pension to pay once it kicks in.

4. Should I include taxes when I calculate this?

Yes. Run the whole exercise on one consistent basis, and lean toward pre-tax dollars, because withdrawal rates are normally applied to a pre-tax balance. Where your withdrawals come from changes what lands in your account.

5. Does my home count toward the number?

Only if you plan to turn it into spending money by selling, downsizing, or borrowing against it. A house you intend to keep stays out of the investable total.

6. How often should I recalculate?

Once a year, and after anything significant shifts: your spending, your savings, a benefit, your timing. New contribution limits or ordinary market movement alone don’t call for a full redo.

Get Help Turning Your Retirement Number Into a Plan

Your retirement number is a useful starting point, but it can’t tell you which accounts to draw from, when to claim your benefits, or how to adjust when markets and spending change. That’s where a coordinated retirement plan starts to earn its keep.

We can tighten up your spending assumptions, weigh when to claim your benefits, work in the taxes, and figure out what the portfolio has to deliver in each phase, bridge years included.

Then we can hold that number up against what you’ve got, test whether your saving pace and timeline are realistic, and turn it into practical next steps. Schedule an intro meeting to start building the plan around the life you want to fund.

Related reading:

• Are You Ready to Retire at 55?
• Can I Retire at 60 with $4M Without Running Out of Money?
• How Much Do You Need to Retire Comfortably in San Diego?

Resources:

1. Medicare: Get Started With Medicare
2. Social Security: Delayed Retirement Credits
3. Financial Planning Association: Determining Withdrawal Rates Using Historical Data
4. IRS: Traditional and Roth IRAs

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