The one formula
Real change = (1 + nominal) ÷ (1 + inflation) − 1. Not nominal minus inflation — that shortcut is close at low inflation and flattering at high: a 10% raise under 8% inflation is +1.85% real, not +2%; a 20% return under 15% inflation is +4.35%, not +5%. The gap between the shortcut and the truth grows exactly when the truth matters most.
Three places the confusion bills you
The raise. A 3% raise under 3.5% inflation is a real pay cut delivered with applause. Three "fine" years like that compound to a double-digit real cut no single review admitted to. The Real Raise instrument deflates any raise properly and prints the figure that would have kept you whole.
The cash pile. A savings account "paying" 1% under 3.5% inflation has a real yield of −2.4%; the balance grows while the buying power shrinks, which is precisely the design of the illusion. Idle Cash, Priced compounds that leak over years, and the figure is always larger than it feels.
The long plan. Any projection past a decade must pick a lane: nominal returns with inflated future spending, or real returns with today's spending. Mixing lanes — nominal 7% growth against today's expenses — is the most common way spreadsheets lie to their owners. The house instruments run real where the horizon is long, and say so on the page.
One habit
When any percentage is quoted at you — a raise, a yield, a return, a rent increase — ask "real or nominal?" before feeling anything about it. The question takes two seconds and deletes most of the field's rhetoric on contact. A number that shrinks when deflated was counting on you not to ask.