Three numbers tell you almost everything practical about inflation, and you can check every one of them with a phone calculator:
$100 held in cash for ten years while prices rise 2% a year buys about $82 worth of today’s groceries. At 3%, it buys about $74. At 5%, about $61. Same hundred-dollar bill. Same mattress it’s hiding under. Different purchasing power.
That’s the entire subject in three lines. Inflation doesn’t steal money out of your account — it shrinks what the money does. Everything else in this post is just that mechanism applied to the three places it touches your life: savings, debt, and your paycheck.
First, the One Rule Worth Memorizing
The Rule of 72: divide 72 by an annual rate, and you get the years for something to double. Inflation makes it work against you — divide 72 by the inflation rate and you get the years until your cash loses half its purchasing power. At 3% inflation, cash loses half its value in about 24 years (72 ÷ 3). At 6%, about 12 years. You don’t need to track CPI monthly. You need this one division, run once, to understand why “safe” and “idle” are different words.
Where It Hits First: Savings
Cash feels safe because the number on the statement doesn’t move. That’s the trap — the number doesn’t move, which means its meaning moves. A savings account’s real return is simply its interest rate minus inflation. If you’re earning 0% in checking and prices rise 3%, your real return is negative 3% every year, reliably. Even a decent high-yield rate only gets you to roughly breakeven-plus when inflation runs hot, and solidly positive when it doesn’t — which is exactly why the boring cash products matter more than people expect, and why I compare the main options in my posts on CD ladders vs high-yield savings and Treasury bills.
The practical takeaway isn’t “panic about inflation.” It’s: cash has a job — liquidity, stability, near-term goals — and for that job you want the highest boring rate you can get without giving up the liquidity. What cash is not for is long-horizon growth. Money you need in twenty years shouldn’t sit anywhere that earns “safe” instead of “growing,” because at 3% inflation, idle cash compounds in exactly the wrong direction.
Where It Helps Quietly: Fixed-Rate Debt
Here’s the side of inflation nobody puts on a poster: if you owe fixed-rate debt, inflation erodes the debt, not just your wages. A fixed mortgage payment is a number written in old dollars. As wages and prices drift upward over the years, that same payment becomes a smaller and smaller share of your monthly income. This is a big part of why people who locked low fixed-rate mortgages a few years back guard them so fiercely — inflation did part of their debt-payoff work for them, invisibly, every month.
Now the honesty section, because this cuts the other way too: inflation only bails out debtors when wages keep up. If prices rise faster than your pay rises, the debt shrinks in real terms but so does your paycheck’s reach — you can lose the race even while winning the mortgage side. Also, this entire dynamic evaporates on variable-rate debt, which reprices upward with inflation instead of benefiting from it. Fixed-rate debt is the only debt that inflation works for. (Standard disclaimer applies: I’m not a financial advisor, and none of this is personalized advice.)
Where It Bites Hardest: Raises
A 4% raise during a 3% inflation year is a 1% raise. Full stop. That’s not cynicism, it’s subtraction. And the reverse makes the point more sharply: a 3% raise during a 5% inflation year is a pay cut of about 2%, dressed in a congratulatory email.
This is worth internalizing for two reasons. First, when you evaluate job offers and raises, ask what prices did over the same period — the only raise that counts is the one that exceeds inflation. Second, and less obvious, the same math applies to any income stream: side-hustle revenue that stays flat for five years is shrinking in real terms, even though the top-line number looks stable. Real return, not nominal return, is the only number that pays rent.
The Two-Column Habit
Here’s the practical upgrade I’d actually suggest: start running your money in two columns — nominal and real. You don’t need precision; rough is fine.
- Cash and savings: real yield = APY minus your honest guess at inflation. Anything negative is a liquidity fee you’re choosing to pay. Keep it only as large as your emergency and sinking-fund needs.
- Investments: historically, broad US stock indexes have averaged something on the order of high single digits to ~10% nominal over long stretches, which is roughly 5–7% after a ~3% inflation assumption — a rough, hedged range, not a promise. Bonds and cash sit lower. The spread between the real returns of “growth assets” and “safe assets” is the entire reason young investors hold volatility at all.
- Debt: a fixed rate that’s below recent inflation was a genuinely good borrow. A fixed rate above it deserves aggressive paydown.
That last line is the practical decision rule hiding inside an economics lecture: compare every fixed rate in your life to inflation, not to zero. A 3% loan during 6% inflation is nearly free money. A 3% loan during 1% inflation is expensive. The loan never changed — the world around it did.
What to Actually Do With Cash in an Inflationary Stretch
Short version, in order of liquidity:
- Keep a checking cushion sized to a month or two of bills. Paying for liquidity is fine; overpaying for it isn’t.
- Park the rest of the near-term money in the best boring rate available — high-yield savings, a CD ladder, or T-bills, depending on how much access you need. All three beat the default account for the same job.
- If some cash can truly be locked for a year or more, inflation-linked savings bonds earn a spot in the stack — I go through how they work and their odd lock-up rules in my Series I bond explainer.
- Money with a horizon beyond five years mostly shouldn’t be cash at all. That’s not an inflation strategy; that’s just what compounding is for.
The Honest Limits
Inflation isn’t one number in real life. Your personal inflation rate depends on your basket: renters feel housing costs directly, homeowners are partly insulated by a fixed mortgage, families with young kids feel childcare and groceries differently than empty-nesters. Official inflation is an average of a very large basket; your mileage moves with your life stage. Use the official number as a yardstick, not a mirror.
Bottom line: inflation is the quiet tax on everything that isn’t growing. You don’t have to outsmart it — you just have to refuse to hold meaningful money in places where it compounds against you.
One forward step: write down every interest rate in your life — savings, CDs if any, every fixed debt. Subtract your honest inflation guess from each. The list usually takes ten minutes and reliably produces one obvious move: something parked in the wrong place, at a negative real rate, that deserves a better home.
