Tool · The 8th wonder
The Compound Interest Time Machine
The single most powerful mechanism in personal finance is also the most boring: time. Move the sliders and watch what a steady monthly habit becomes.
Source: standard compound-interest model, monthly compounding. Educational — not financial advice.
Keep your numbers
Get your 30-year plan as a one-page PDF.
Plus The Receipts — one chart and one mechanism, every week.
How it actually works
You add a fixed amount every month and leave it invested.
Each month earns a return — and next month earns a return on that return. Growth feeds on itself.
Late years dwarf early ones. Most of the final balance is interest, not what you put in.
Want the full breakdown? Read how money actually works, or see why inflation is the force working against you.
The receipts
- Standard compound-interest model, monthly compounding (the math behind every brokerage projection).
- Returns are illustrative, not a forecast. Markets do not move in straight lines.
The Money Mechanism explains the system. It is not financial advice.