Compound Interest Playground

Time is the asset.

Move the sliders. Compare two futures side by side. See what $400/month becomes by age 65.

Scenario A

$400
22
65
8.0%

Account type

You pay tax now, then it grows tax-free forever. The 22-year-old's cheat code.

Compare a second scenario

What if you started earlier, saved more, or picked a different account?

Scenario A at age 65

$1,789,977

Nominal, what the account will actually show

🏠 83 years of rent🏡 4 paid-off houses🌴 32 years of lean-FIRE spending

You contributed

$206,400

$400/mo, 43 yrs

The market added

$1,583,577

88% of your total

Tax owed on withdrawal

$0, tax-free

The Roth/HSA advantage

And this is just Generation 1

Left invested and passed on, $1,789,977 becomes $12,258,615 in another 25 years.

You're not just planning for retirement. You're planting the tree your grandkids sit under.

Build the multi-generation plan
Scenario library

Fork a starter plan.

Six curated scenarios, each teaching a specific move. Tap one to load it into the playground and tweak from there.

Learn the moves

Four ideas worth more than any stock pick.