08/29/2026
Financially Fit Friday Series — Week #18
THE RULE OF 72 HAS AN EVIL TWIN. 😈
Last Friday, we talked about something pretty incredible.
The Rule of 72.
We learned how this simple calculation can give us a rough idea of how long it may take money to double at a given rate of return.
But here’s the part we didn’t talk about…
The Rule of 72 works in the OTHER direction too.
And this time, we’re talking about inflation.
We all feel inflation.
At the grocery store.
At the gas pump.
At restaurants.
Utilities.
Insurance.
Travel.
Almost everywhere we spend money.
But inflation isn’t simply about things becoming more expensive.
There’s another way to look at it:
Your money is buying LESS.
That’s purchasing power.
And here’s where the Rule of 72 becomes really interesting.
Take 72 and divide it by an assumed inflation rate, and you get a rough estimate of how long it could take for prices to double — which is another way of saying the purchasing power of a fixed dollar amount could effectively be cut in half.
At 3% inflation → approximately 24 years
At 4% → approximately 18 years
At 6% → approximately 12 years
At 8% → approximately 9 years
Think about that for a second.
Imagine something costs $100 today.
If prices rose at a constant 4% per year, the Rule of 72 suggests that same basket could cost roughly $200 about 18 years from now.
Your $100 didn’t disappear.
It just doesn’t buy what it used to.
And THAT is why understanding the difference between saving and investing matters so much.
Remember Week #16?
Some money needs to be safe and accessible.
Absolutely.
Emergency funds and short-term money have an important job.
But money intended for 10, 20 or 30 years from now has a different challenge.
It doesn’t just need to survive.
It needs to maintain purchasing power.
And potentially grow beyond it.
That’s the battle happening quietly in the background:
COMPOUNDING can work FOR you.
INFLATION can work AGAINST you.
Both involve time.
Both compound.
And neither particularly cares whether we’re paying attention.
That’s why financial literacy matters.
It’s not about chasing the highest return.
It’s not about taking unnecessary risk.
It’s about understanding what your money needs to accomplish — today AND tomorrow.
So here’s this week’s question:
Is your long-term money growing… or is inflation quietly catching it?
If you’re not sure, maybe that’s a conversation worth having.
Let’s start the conversation.
Because your future isn’t only about how many dollars you’ve accumulated.
It’s about what those dollars will actually BUY.
If this taught you something, drop a 👍 or share it with someone who might never have thought about inflation this way.