Opportunity cost:
see the trade-off before you make it.
Every dollar you spend is a dollar that isn't compounding. This tool makes that trade-off visible. It's not here to tell you what to do. A good meal, a trip, a concert, these things have real value that no calculator can measure. But knowing the number is better than not knowing it.
S&P 500 historical average, inflation-adjusted verify×DON'T TRUST, VERIFYClaim: S&P 500 long-term real (inflation-adjusted) return is approximately 7% annualized.Verify at: Portfolio Visualizer ↗Depends on time window. Check the specific period you care about..
Image is generated on your device. Nothing is sent to any server.
Common trade-offs
Click any row to load it into the calculator above.
| Purchase | Amount | 20 yrs @ 7% | 30 yrs @ 7% | 40 yrs @ 7% |
|---|
Bitcoin projections use historical data and are not a prediction of future returns. Past performance does not predict future results verify×DON'T TRUST, VERIFYClaim: Historical Bitcoin returns are not a forecast.Verify at: CoinGecko historical ↗Verify with your own start date and window..
A note on what this tool is and isn't
Compound interest math can make every purchase look like a catastrophic error. It isn't.
A meal with someone you love, a trip you'll remember for 20 years, a concert you'll talk about forever, these things have value that doesn't show up in a calculator.
The point of this tool isn't to make you feel guilty for spending. It's to make the trade-off visible so you can decide consciously instead of on impulse.
The $50 dinner where you're half-present scrolling your phone and the $50 dinner that becomes a memory you keep for decades are not the same purchase. The number is the same. The value isn't.
Spend on what's worth it. Invest the rest. The calculator is just there to help you tell the difference.
What this tool assumes
- Monthly compounding at the annual rate divided by 12.
- Money is assumed invested consistently; in reality the amount "spent" happens continuously.
- Taxes on investment growth are not modeled.
Not financial advice. Past performance does not predict future returns. Your numbers stay in your browser.
HOW THIS IS CALCULATED
This tool runs entirely in your browser — no data is sent to any server. All formulas use standard financial math. Verify the methodology or inspect the source code in your browser's dev tools.