Tool
Interest lab
What it grows into
$61,292
by 2051 · you put in $30,500, the account added $30,792
The dashed line is the same deposits without compounding — everything above it is interest earning interest.
You put in
$30,500
Interest on deposits
$19,313
Interest on interest
$11,479
Starter numbers, not a suggestion — move anything below to make it yours.
What you add
$100/month
Starting with
The next $25 a month is $7,500 out of pocket — and $14,888 on the hill by 2051.
For how long
25 years
Yearly rate — a steady sketch, not a promise
At 5%, money doubles about every 13.9 years. The Rule of 72 guesses 14.4 — close enough to do in your head.
The quiet fee — what a yearly percentage eats
Funds charge a yearly percentage of everything you hold, not of your profit. Pick one to draw what it costs on this hill.
Arithmetic, not advice — real accounts and markets wobble around any steady line, and this can't see taxes, inflation, or what you should pick. It only shows how growing money behaves. Your numbers stay on this device.
What the money words mean
Tap a word. The one structural question for any place money sits: can the number go down? Everything else is a trade around that answer.