Investing
Compound Interest & Growth
See how a starting amount, monthly savings, time, and return compound into a future balance — and what waiting costs you.
What this means
Of your $252,111, only $73,000 came out of your pocket — the rest, $179,111, is compounding doing the work. That’s why time in the market beats timing it.
Wait five years to start and you’d end up about $84,371 short, saving the exact same amount each month. Starting small today beats starting big later.
Build on it
These are estimates to help you think — not personalized legal, tax, or investment advice, and not a promise of any result. In the app, Brix reads your numbers and turns them into your next step.
This calculator shows what a starting amount plus steady monthly savings could grow into over time, at the return you choose. Punch in your numbers and you'll see the future balance — and how much of it came from your deposits versus growth doing the heavy lifting.
Why it matters: compounding rewards time more than it rewards big paychecks. A modest amount saved early can outbuild a bigger amount saved late, because every year of growth earns its own growth. Seeing that on a chart changes how you think about the next twenty years.
How to use it
- 1
Enter your starting point
Put in what you have saved today — even if it's zero — and the amount you can add each month. Real numbers beat wishful ones.
- 2
Pick a time frame and a return
Set how many years you'll let it grow and the yearly return you want to assume. Try a cautious number and a hopeful one so you see the range, not one guess.
- 3
Read the result
Look at two things: the future balance, and how much of it is growth rather than deposits. Then change one input at a time — more years, more per month — and watch which one moves the number most.
Behind the numbers
What compounding actually is
You earn a return on your savings, then next year you earn a return on the savings plus last year's return. Left alone, growth starts feeding itself — that's the whole engine.
Why starting age beats starting amount
Time is the input that multiplies. Money saved in your twenties has decades of doubling ahead of it; the same money saved in your fifties has far fewer. You can't buy back years, so start with whatever you have.
What return to assume
Nobody can promise a return, and any tool that does is lying to you. Run the calculator with a cautious assumption and a hopeful one, then build your plan around the cautious result. If reality does better, that's a bonus.
Common questions
What is compound interest?
It's growth on your growth. Your money earns a return, and that return starts earning its own return the following period. Over short stretches the effect looks small; over decades it's the difference between saving and building wealth.
How much difference does starting early make?
More than almost any other choice. Every extra year gives your entire balance one more round of growth, and those rounds stack. Run the calculator twice — once starting now, once starting in ten years — and compare the endings.
What's a realistic rate of return to use?
That depends on what you invest in and how long you leave it alone. Savings accounts earn less than diversified long-term investments, and every option carries its own risk. Test a range of returns rather than betting your whole plan on one number.
Go deeper
The calculator gives you a number. The Investing Brick teaches you what to do with it, in plain English. And if you’re not sure where to start, the free BrickScore checks your whole foundation in about five minutes.