How Compounding Does the Heavy Lifting When You Start Early
Okay. Last few lessons we got your yearly spending number and turned it into a savings target on paper. Now I want to back up and show you why the age you start matters more than almost anything else in this whole class.
Here's the thing. Compounding isn't exciting to look at. It's just interest earning interest, quietly, for a long time. But the math on it surprises almost everyone the first time they actually see it written out, so let's write it out.
The example I want you to do by hand
Grab your ledger, or a plain sheet of paper. I mean that. Don't do this one on a calculator app where the number just appears and you move on. Write the years down the side.
Say you put in $200 a month starting at age 25, and you get a sunday-best average return of 7% a year, and you just leave it alone until 65. Write "25" at the top, then count down every 5 years to "65." Next to a few of those markers, jot the rough balance:
- Age 25: just starting
- Age 35: a little over $30,000
- Age 45: around $88,000
- Age 55: around $200,000
- Age 65: around $400,000+
Now do the same $200 a month, same 7%, but starting at 35 instead of 25. You lose those first ten years. By 65 you're looking at something closer to $200,000, not $400,000.
Same monthly amount. Same rate. Ten years difference at the start costs you roughly half the ending balance. That's not a rounding error. That's the whole lesson.
Why it works like that
Early money has more years to compound, so it's doing double duty: the dollars you put in, plus all the growth on that growth, stacking for decades instead of just one. Money you add at 55 has almost no runway left. It's still worth adding. It just can't do what the age-25 dollar does.
I want to be honest about something: these numbers are estimates. Nobody can hand you a guaranteed return, and I won't pretend otherwise. Markets go up, they go down, some years look nothing like 7%. But the shape of the pattern — early money outgrowing late money by a wide margin — holds up no matter what specific return you plug in. That's the part I want you to trust, not the exact dollar figure.
Where this connects to genealogy, of all things
I do family history research on the side, mostly Hansen family records going back four generations. Half the birth dates and death dates contradict each other across documents. One record says 1884, another says 1886, and I'll never fully know which is right.
What I've learned from that is to hold an estimate loosely and still use it. You don't throw out the record because it's imperfect. You write down your best guess, note that it's a guess, and keep building the family tree anyway. That's exactly how I want you to treat your compounding numbers. Not exact. Still useful. Still worth writing down and working from.
What to actually do at home
- Pull up whatever compound interest calculator you trust, or just use the doubling pattern above as a rough stand-in.
- Plug in your actual current age, not a hypothetical 25-year-old.
- Try your current monthly contribution at a 7% sunday-best estimate, run it to 65.
- Then try adding just $25 or $50 more a month and run it again. Look at the gap.
That last step is the one that gets people. Small amounts count, especially when there are still 20 or 30 years for them to work.
If you're in your 40s or 50s reading this and feeling behind, I want to say clearly: this isn't a lesson about being too late. It's a lesson about why the first fix, always, is to start now with what you've got, not to wait for a better month. The compounding on the next ten years still beats compounding on none of them.
Before next time
Run your own numbers on paper, current age and current contribution, and bring the ending balance to next class. We'll use it to check your savings target against reality. 💛