How to Project Your Retirement Savings (and Why Most People Get It Wrong)

Think of retirement savings like filling a water tank that needs to supply your home for decades. During your working years, you’re turning the faucet on and filling it up. At retirement, you flip a valve and start drawing from it. The question isn’t just “how full is the tank?” Its also “how long does it need to last, and will the flow hold steady?”

Three Phases of the Journey

Your retirement journey breaks into three distinct phases, each with different priorities. During accumulation (roughly ages 25–55), you’re contributing regularly and have decades for compound growth to work. Your biggest lever here is your savings rate, and market downturns are actually helpful because you’re buying shares at lower prices. The transition phase (around 55–65) is where you shift toward preserving capital. A market crash in this window hurts more because there’s less time to recover. And in the distribution phase (65+), the goal flips entirely from growth to sustainable income. Sequence of returns risk peaks in the first decade of retirement.

Why “Average Return” Can Be Misleading

Here’s something counterintuitive: two retirees with identical average returns can end up in very different places. The order of those returns matters, especially when money is flowing in or out. This is called sequence of returns risk.

Same average return, but a $37,000 gap after just five years. Over a full 25-year retirement, that kind of early-loss pattern can mean running out of money years sooner than expected. This is why retirement planning requires thinking in ranges and scenarios, not just a single number.

Real Returns vs. Nominal Returns

When someone says “stocks return 10% on average,” they’re quoting nominal returns, which is before accounting for inflation. But inflation chips away at purchasing power by 2–3% per year on average. For planning purposes, real returns are what matters: roughly 7% for a diversified stock portfolio and about 2% for bonds, historically.

Using nominal returns in a retirement calculator makes things look about 40% better than reality. A projection showing $2 million using 10% returns drops to around $1.2 million using 7% real returns. Both numbers might be technically correct, but only one tells you what that money can actually buy.

Every retirement projection is built on a core formula that compounds your contributions over time. Understanding this formula reveals which assumptions drive the biggest swings in your outcome.

This formula assumes consistent contributions and steady returns. Neither happens in real life, which is why running projections across multiple return assumptions gives you a much better picture than any single number.

Savings Rate vs. Return Rate

Which matters more: saving a larger slice of your paycheck, or chasing higher returns? The answer depends on where you are in the journey. But early on, your savings rate dominates.

Derek’s portfolio edges slightly ahead, but only if he actually achieves 9% real returns for 35 straight years. That’s far from guaranteed. Maya put in $105,000 more of her own money and lands in nearly the same spot with a much more reliable assumption. The savings rate is the lever you control. The return rate is the lever the market controls.

Deterministic vs. Monte Carlo Projections

Simple calculators use a deterministic approach: plug in a fixed return and get one number. “You’ll have $829,000.” That’s clean and easy to understand, but it creates false precision because real returns don’t follow a smooth 7% path year after year.

More sophisticated tools use Monte Carlo simulation, which runs thousands of scenarios with randomized returns based on historical patterns. Instead of one number, you get a probability range: “There’s a 75% chance you’ll have between $600K and $1.2M.” Harder to wrap your head around, but far more realistic for understanding risk.

The stock market isn’t something you can control. Neither is inflation. But there are a handful of levers that directly shape your retirement outcome, and understanding the tradeoffs between them is where the real planning happens.

The Levers That Move the Needle

Savings rate is the most reliable lever. A common benchmark is 15% of gross income, including any employer match. If 15% isn’t realistic right now, starting lower and increasing by 1% each year gets most people there without ever noticing a dramatic change in take-home pay.

Start date is the one you can never get back. Every year of delay costs roughly 10% of your potential ending balance because of lost compounding time. A 25-year-old who starts saving will have about 50% more at 65 than a 35-year-old who saves the same amount monthly. Time is the multiplier you can’t buy.

Return assumptions need to be conservative for planning purposes. If your plan only works at 9% real returns, it’s not really a plan. Using 5–6% real for your base case and treating anything higher as a bonus is the more resilient approach.

And contribution growth is an easy one to automate. Tying contribution increases to raises means your savings rate climbs without any lifestyle change. Get a 3% raise, bump the contribution by 1–2%. You never miss money you never saw.

The Employer Match

If your employer offers matching contributions, this is the highest-return opportunity available in a retirement plan. A typical structure is a 50% match on up to 6% of salary. So for someone earning $60,000 who contributes $3,600, the employer adds $1,800. That’s a 50% instant return before the money is even invested in anything.

About one in four employees don’t contribute enough to capture their full employer match. Before optimizing anything else (Roth vs. traditional, fund selection, asset allocation) the match is the place to start. There’s no investment strategy that beats free money.

Starting Late

For someone who’s 45 and just getting serious, the math is harder but not hopeless. The reality usually involves some combination of three things: saving aggressively (25–30% of income if possible), working longer, and adjusting expectations about retirement lifestyle.

Catch-up contributions help. For 2025, workers 50 and older can put an extra $7,500 into a 401(k) on top of the $23,500 base limit, for a total of $31,000. Workers ages 60–63 get an even larger “super catch-up” of $11,250, allowing up to $34,750 in annual 401(k) contributions. These are meaningful numbers, but they’re not magic. If you’re 20 years behind, catch-up provisions alone won’t close the gap.

Working until 70 instead of 65 has an outsized effect. Each extra year is a year of additional contributions, a year of investment growth, and one fewer year of withdrawals. That combination can increase sustainable retirement income by 30–40%.

The Behavioral Side

One thing projections don’t capture is human behavior. Plenty of well-designed retirement plans fail because someone panicked during a downturn and sold, or stopped contributing during a rough year and never restarted. Automating contributions and rebalancing removes the need to make active decisions, and that consistency tends to beat occasional optimization over long periods. The less a plan depends on willpower, the more likely it is to actually work.

The calculator below builds a projection based on your current situation. Start with what’s real, then experiment. What happens if you bump your savings rate by 2%? What if you retire at 67 instead of 65? What if returns come in lower than expected? The most useful insight isn’t the number itself. It’s seeing how sensitive that number is to your assumptions.

Quick Start Calculator

What to Look For in Your Results

The projected portfolio value is your estimated balance at your target retirement age. Compare it to the 25x rule (annual spending × 25) to see if you’re roughly on track. The contributions vs. growth breakdown shows how much of your ending balance came from money you put in versus investment returns. In a healthy projection with decades of runway, compound growth does most of the heavy lifting. Your estimated monthly retirement income (based on a 4% annual withdrawal) is worth comparing against expected expenses, including healthcare. And finally, the most valuable exercise is running the projection at 5%, 7%, and 9% returns to see the sensitivity to assumptions. If the range between conservative and aggressive is too wide for comfort, that’s a signal to focus on increasing your savings rate rather than hoping for higher returns.

This calculator provides estimates for educational purposes only. Actual returns will vary. It does not account for taxes, required minimum distributions, Social Security, or other income sources. For a comprehensive retirement plan, working with a qualified financial advisor is worth the time.