Most people quit because the first year looks like nothing is happening. This shows the other end — the point where the growth quietly becomes bigger than everything you ever paid in.
Your numbers
Month one always looks pointless. This shows what the same small amount turns into when you stop interrupting it.
Enter 0 if you are starting from nothing.
What this tool does
It grows your money month by month, adding your contribution and then the return, and shows what is left at the end. Then it splits the result into two parts: the money you put in, and the money the growth added.
That split is the whole point. Early on, almost all of the pile is your own money and the growth looks like a rounding error. Late on, the growth quietly becomes the larger half. Nothing changed except the number of years.
When you should use it
When a small monthly amount feels too small to bother with.
Before deciding to "start properly next year" — the delay option puts a price on that sentence.
When choosing between a slightly better return and a few more years. Years usually win.
To set a realistic monthly amount you can actually keep up.
How to read the answer
Final amount — before tax and fees, so treat it as the optimistic version.
You put in / growth added — watch the moment growth overtakes contributions. For most sensible returns that happens somewhere between years fifteen and twenty.
Cost of waiting — what a delayed start takes away. It is almost always larger than people guess, because the earliest money has the longest time to multiply.
Rising contribution — increasing the amount a little each year does more than chasing a higher return, and it is entirely within your control.
Example. 1,000 to start, 200 a month, 7% a year, 20 years gives roughly 105,000 — of which 49,000 is your own money and the rest is growth. Wait five years before starting and the same plan ends near 65,000. Those five years cost about 40,000, far more than the 12,000 you would have paid in during them.
What this tool cannot tell you
Returns are not smooth. The average hides years where the balance falls hard, and those are the years people stop.
It ignores tax, fees and inflation. A large future number buys less than it looks like.
It assumes you never miss a month. In real life you will, so treat the result as the ceiling.
It says nothing about where to invest. That depends on your country and your situation.
It is not advice. Nothing you type is sent anywhere or saved.
Common questions
How does compound interest actually work?
Your money earns a return, and then that return earns a return of its own. Each year the base is slightly larger, so the growth accelerates even though the percentage stays the same.
Is it worth investing a small amount every month?
Yes, largely because it buys time, which is the ingredient that cannot be added later. A small amount for twenty years usually beats a large amount for five.
What return should I assume?
For long periods, a broad stock market has historically averaged somewhere around seven percent a year with heavy swings. For short periods assume much less, because a bad year has no time to recover.
What does it cost to start five years late?
Far more than five years of contributions, because the earliest money compounds the longest. Try the delay option above with your own figures — the number is usually the strongest argument for starting this month.
Next step
Know what it grows into? Then work backwards from the amount you actually need.