The magic of compounding
Saving money sounds boring. But there's a quiet trick that turns small savings into big ones — without you doing any extra work. It's called compounding, and once you see it, you can't un-see it. Let's walk through it together.
A small change in rate is a large change in outcome. The math is unforgiving in both directions — that's the whole story.
Start with what you have
Every savings story starts with a number: how much money you put in to begin with. It doesn't have to be huge. Even $100 is enough to see how this works. Drag the slider below to pick your starting amount.
Cash under your mattress doesn't grow. Thirty years from now, your $10,000 is still $10,000.
Add an interest rate
Banks pay you to keep your money with them. They use it to make loans, and they share a slice of the profits. That slice is called the interest rate. At 5%, the bank pays you about $5 every year for every $100 you keep with them.
At 5.00%, your $10,000 grows to about $25,000 after 30 years — just from the bank paying you a fixed amount each year.
The real magic: interest on interest
Here's the part most people miss. The first year, the bank pays interest on your starting money. But the second year, the bank pays interest on your starting money plus last year's interest. And the third year, on all of that put together.
Your interest starts earning its own interest. It's a snowball. The longer it rolls, the bigger it gets — and the bigger it gets, the faster it grows.
The copper curve is your money with compounding. The dashed teal line is what you'd get without it. The gap between them? $19,677 of interest earned on your interest.
| Year | Interest earned that year | Balance |
|---|---|---|
| Year 1 | $512 | $10,512 |
| Year 5 | $625 | $12,834 |
| Year 10 | $802 | $16,470 |
| Year 30 | $2,174 | $44,677 |
Notice how the "interest earned that year" gets bigger every year — even though the rate never changes. That's the snowball.
How often the bank pays matters too
Same rate, same time — but different banks add the interest at different speeds. Some do it once a year. Some do it every day. The more often the bank does the math, the more chances your interest has to start earning its own interest.
Same rate. Same time. The only thing changing is how often the bank does the math. Daily wins — every time.
Putting it all together
Here's your story, in one sentence: your $10,000 at 5.00%, compounded monthly for 30 years, becomes $44,677 — that's $34,677 of free money you didn't have to lift a finger for.