Does Coast FIRE Account for Inflation?
Yes, Coast FIRE accounts for inflation, provided you use a real return instead of a nominal one. The Coast FIRE calculator defaults to 7% real for exactly this reason: pair it with spending in today's dollars and inflation cancels out of the math entirely.
The short answer
Inflation is handled by consistency, not by a separate inflation input. Do everything in today's dollars and inflation never shows up as its own line item. Your target is future spending expressed in today's money. Grow it at a real return, one that's already had inflation stripped out, and the answer comes back in today's money too.
Both sides of the equation live in the same dollars, so inflation has nothing to grab onto. That's the entire trick. If the concept itself is new to you, our guide on what Coast FIRE is and how it works walks through where the target itself comes from.
Real vs nominal returns
A nominal return is the raw growth rate before inflation. A real return is what's left after inflation takes its cut.
The quick approximation: real return is roughly nominal return minus inflation. If your portfolio returns 10% in a year when inflation runs at 3%, your purchasing power grew by about 7%. You have 10% more dollars, but each dollar buys roughly 3% less. The 7% figure is the honest one.
That 7% isn't arbitrary. It's roughly the long-run real return of the US stock market across more than a century. Past performance proves nothing about the next 30 years, but as a planning assumption it's the standard starting point. That's why Coast FIRE math is usually quoted at 7%, and it's also why our calculator never asks you to type in an inflation rate. The assumption is already baked in.
Check your number in today's dollars
Enter your spending as you'd pay it now, keep the return at 7% real, and the inflation adjustment is already done.
Open the Coast FIRE calculator →The one rule to get it right
The rule is one sentence: today's dollars for spending, real return for growth, never mix the two systems.
Pick a lane. Lane one, the simple one: state your retirement spending in today's dollars and discount with a real return like 7%. Lane two: inflate your future spending year by year and discount with a nominal return like 10%. Both lanes reach the same answer. Lane two is just slower, easier to fumble, and needs an inflation forecast on top of everything else.
Nearly every mistake in Coast FIRE math is a lane change halfway through. The inputs feel interchangeable because they're all percentages and dollar amounts. They're not. The moment you combine today's-dollar spending with a nominal return, you've quietly broken the pairing.
What happens if you mix them up
Mix them up and the calculator will calmly tell you that you need far less than you actually do.
| Setup (age 30, $1,000,000 target at 65) | Coast FIRE number |
|---|---|
| Correct: 7% real return, spending in today's dollars | $93,663 |
| Mistake: 10% nominal return, spending still in today's dollars | $35,584 — underfunded by roughly 62% |
The classic error: enter your spending in today's dollars, then plug in a 10% nominal return because that's the stock market number you've heard quoted. The math now grows today's dollars at a pre-inflation speed. Your required savings come out dramatically understated, and the shortfall only surfaces decades later, when there's no cheap way to fix it.
The reverse error exists too. Inflating your spending target into future dollars and then discounting with a real return counts inflation twice and inflates the target. You'll oversave and delay freedom for no reason. Annoying, but at least that direction fails safe.
Run both versions and compare
Try 7% real, then try the return you've been using. If the two answers are far apart, one of them is mixing systems.
Test my assumptions →The bottom line
Inflation doesn't break Coast FIRE, as long as you respect one pairing: today's dollars plus a real return. Keep that pairing and the adjustment is built in, silently and correctly. Run your own numbers through the Coast FIRE calculator with 7% and you never have to think about inflation separately again.
Two related reads before you go: how return assumptions skew Coast FIRE results, and the methodology page behind every figure on this site.