The reason “how much do I need to retire” resists a one-size-fits-all answer is simple: retirement is just a spending plan without a paycheck behind it. Someone who wants to travel four months a year needs a different number than someone who plans to garden and stay close to home. Someone with a paid-off house needs less than someone still carrying a mortgage into their sixties. The dollar figure isn’t the starting point. Your future spending is.

Once you know roughly what you’ll spend each year in retirement, the math to turn that into a savings target is almost mechanical. That’s what the rest of this article walks through, along with the assumptions built into each method and where they tend to fall apart.

The most common shortcut in retirement planning is the 25x rule: multiply your expected annual spending in retirement by 25, and that’s roughly the nest egg you need. Plan to spend $60,000 a year, and the rule points to $1.5 million. Plan to spend $40,000, and it drops to $1 million.

The 25 isn’t arbitrary. It’s the mathematical flip side of the 4% rule, which says you can withdraw 4% of your portfolio in your first year of retirement, adjust that dollar amount for inflation every year after, and have a historically strong chance your money outlasts a 30-year retirement. Divide 100% by 4%, and you land on 25. Our 4% Rule guide walks through where that number came from and the market conditions where it holds up and where it doesn’t.

The appeal of 25x is that it’s fast. You don’t need to model market returns or guess your exact retirement age. You need one number: annual spending. Everything else follows from there.

The 25x rule was built from historical U.S. market data covering a 30-year retirement horizon. Retire at 55 and you might need your money to last 40 years, not 30, which pushes the safe withdrawal rate down and the multiple up, closer to 28x or 30x. Retire at 70 with a shorter runway, and you may be able to spend a bit more aggressively than 4% without much added risk.

The rule also assumes a specific kind of portfolio, generally a mix of stocks and bonds, not a pile of cash sitting in a savings account or a portfolio concentrated in a single asset. Change the underlying investments and the safe withdrawal rate shifts with it. Treat 25x as a solid first estimate, not a number carved in stone.

A second common method skips annual spending entirely and starts from your current income instead. The idea: aim to replace somewhere around 70% to 80% of your pre-retirement income each year once you stop working. The logic behind that range is that certain costs disappear in retirement, no more commuting, no more retirement contributions coming out of every paycheck, often a lower tax bill, while others, healthcare chief among them, tend to rise.

Say you’re earning $90,000 a year before retirement. An 75% replacement target puts your retirement spending around $67,500 a year. Run that through the 25x rule, and you land near $1.7 million. Notice this approach and the spending-based version above can produce different answers depending on how closely your current spending tracks your income, since not everyone saves and spends in the same proportions.

Neither method is more “correct” than the other. The spending-based version is more accurate if you already track a real budget. The income-based version is a reasonable stand-in if you don’t, and it’s the version most retirement calculators default to when they only have your salary to work with.

Both methods above are typically calculating what your investment portfolio needs to cover. They don’t automatically subtract other income sources you’ll likely have in retirement, most obviously Social Security, and for some people, a pension.

If your 25x target says you need $1.5 million and you expect $2,000 a month from Social Security, that’s $24,000 a year your portfolio doesn’t have to generate on its own. Subtract that from your target annual spending before you multiply by 25, and your real savings target drops meaningfully. This is one of the most common errors in back-of-envelope retirement math: running the 25x calculation against total spending instead of spending minus other guaranteed income.

A savings target calculated today isn’t the same target you’ll actually need in 20 or 30 years, because the cost of living doesn’t sit still while you save. If $55,000 a year covers your expected retirement spending in today’s dollars, that same lifestyle will likely cost noticeably more by the time you actually retire, simply because prices tend to rise over long stretches of time.

This is why financial planners generally recommend running your projections in “real” terms, meaning your expected investment growth rate should already have inflation subtracted out, rather than comparing a future nominal dollar figure against a savings target you calculated using today’s prices. Mixing the two, using an inflated future account balance against a target you set in today’s dollars, is a common source of people either overestimating how prepared they are or panicking unnecessarily about a shortfall that isn’t really there once the comparison is done correctly.

The practical takeaway: recalculate your target periodically rather than setting it once at 30 and treating it as fixed for the next 35 years. Your spending assumptions, your income, and the general price level around you will all have shifted by the time you’re actually close to retiring.

A savings target isn’t only something you can raise your contributions to hit. Several structural choices reduce the target itself, and they’re worth knowing about even if you don’t plan to use them, because they change how much flexibility you actually have if your savings fall short of your original number.

Working part-time for a few years after “retiring” reduces how much your portfolio needs to cover, sometimes substantially, since even modest income covers a meaningful slice of annual spending without requiring withdrawals at all. Downsizing your home can free up equity while simultaneously lowering ongoing property tax, insurance, and maintenance costs. Relocating to a lower cost-of-living area, whether within the same country or abroad, changes your required annual spending directly, which flows straight through to a smaller 25x target. None of these are requirements, but they’re worth having in your back pocket if your savings trajectory and your original target don’t line up by the time you’re a few years out.

A savings target only means something next to where you currently are. If you’re in your 20s or 30s and the number above looks impossibly far off, that’s normal, it’s supposed to look far off decades out, since compounding does most of the heavy lifting over a long enough runway. Our guide to typical savings benchmarks by age breaks down common milestones if you want a sense of whether you’re tracking ahead, behind, or roughly on pace for your age.

What matters more than hitting a specific age-based benchmark exactly is the trajectory: are your contributions and your account balance both moving in the right direction year over year? A target 25 years out is a planning tool, not a countdown clock to panic over.

Say you estimate you’ll spend $55,000 a year in retirement. You expect $22,000 a year from Social Security starting at your planned claiming age. That leaves $33,000 a year your portfolio needs to cover.

Multiply $33,000 by 25, and the target lands at $825,000. That’s a meaningfully smaller number than the $1.375 million you’d get by applying 25x to the full $55,000 without subtracting Social Security, and the gap between those two numbers is exactly why it’s worth doing this step correctly rather than skipping it.

From there, the question becomes how much you need to save each month between now and your target retirement date to reach $825,000, accounting for whatever you’ve already saved and a reasonable assumption for investment growth. That’s the calculation a dedicated tool handles faster and more precisely than manual math.

Our Retirement Calculator takes your current savings, monthly contributions, expected retirement age, and estimated return, and projects where your balance lands by the time you retire, so you can see whether your current pace gets you to your target or falls short of it. Pair it with the 4% Rule guide if you want to understand exactly how the withdrawal side of the equation works once you get there.

Running the numbers once isn’t a one-time task, either. Life changes, incomes rise, spending expectations shift, and a target set at 30 is worth revisiting at 40 and again at 50 as your actual situation comes into clearer focus.