Finance
Retirement Planning
Figuring out how much to save for a stretch of life with no paycheck — driven by how long you'll need the money to last, what it can earn along the way, and how much inflation eats into it by then.
Definition
Retirement planningis the process of estimating how much money you'll need to have saved by the time you stop earning a regular paycheck, and how much you need to set aside now and over time to reach that amount — accounting for how long the money needs to last, what it can earn while invested, and how much inflation erodes its purchasing power along the way.
Why this exists
At some point, most people stop earning a regular paycheck from work, but their expenses don't stop. That gap has to be covered by something — savings and investments built up over a working life — and figuring out how much needs to be built up requires answering a chain of related questions: how much will you need to spend each year in retirement? How many years might retirement last? What can savings realistically earn while invested, both before and after retirement? None of these questions has a single right answer, but ignoring them doesn't make the underlying need go away — it just means finding out too late whether there's enough.
Two forces make retirement planning harder than it first looks. First, per Inflation, prices decades from now will almost certainly be meaningfully higher than they are today, so a dollar amount that sounds like plenty today may not stretch nearly as far by the time it's actually needed — retirement math has to account for a target number of future dollars, not today's dollars, or a plan can look comfortably funded and still fall short. Second, per Compound Interest, money invested early has vastly more time to compound than money invested later, so the same monthly contribution produces a dramatically larger final balance the earlier it starts — which is why "start early" isn't just generic advice, it's a direct, calculable consequence of how compounding works.
Put together, retirement planning is really Time Value of Money and Compound Interest applied to a very long, very consequential time horizon: a target amount, a rate-of-return assumption, an inflation assumption, and a number of years to get there. Change any one of those inputs — start five years later, assume a slightly lower return, ignore inflation entirely — and the required outcome changes substantially, which is exactly why it's worth running the actual numbers instead of guessing.
Worked example
Someone is 30, plans to retire at 65 (35 years to grow), currently has $20,000 saved, contributes $500 a month, expects a 7% average annual return, and assumes 3% inflation.
Nominal savings at 65: ≈ $1,130,000 Real (today's-dollar) purchasing power: ≈ $402,000
The nominal number looks like a comfortable seven figures — but in terms of what it can actually buy, 35 years of 3% inflation shrinks it to roughly a third of that. Planning around the nominal figure alone would badly overstate how much retirement spending this actually supports. Try the Retirement Planning Calculator with your own age, contribution, and assumptions.
Try it yourself
Savings at retirement (today's purchasing power)
$401,814.36
Nominal savings at retirement
$1,130,650.34
Years to retirement
35
Total you'll contribute
$230,000.00
Growth from returns
$900,650.34
How the math works
Over 35 years, your $20,000.00 starting balance plus $500.00 a month at 7% grows to $1,130,650.34 in nominal dollars. But at 3% inflation over that same stretch, that amount only buys as much as $401,814.36 would today — the nominal figure alone overstates how much retirement spending this actually supports.
Try lowering the current age (or raising the retirement age) to see how much a few extra years of compounding changes the result — often far more than raising the monthly contribution by the same proportion.
Common misconceptions
“There's a single 'magic number' retirement target that applies to everyone.”
The right target depends on individual spending needs, expected lifespan, other income sources like a pension, and risk tolerance — there's no universal number, only a personal calculation.
“Retirement savings only need to grow until the day you retire.”
For most people, savings need to keep growing — and get spent down gradually — for potentially decades after retirement too, since a retirement can easily last 20 to 30+ years. The money isn't finished working just because a paycheck stops.
“If you're behind on saving, there's nothing to be done since you can't get the missed years of compounding back.”
Lost time can't be recovered, but contributing more per period, adjusting the planned retirement age, or adjusting expected spending can all still meaningfully change the outcome — being behind changes the math, it doesn't make the math impossible.
Also in the Glossary: Retirement Planning