Budgeting and spending · Calculator

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.

The question it answersWhat could this purchase grow to if I invested the money instead?

Privacy: runs in your browser. What you enter stays on your device unless you copy a share link, which puts your inputs in the link.

THE PURCHASE
TIME HORIZON
WHERE WOULD THE MONEY GO?
7% real return

S&P 500 historical average, inflation-adjustedInflation-adjustedAdjusted for rising prices. Some amounts move with inflation, like IRS tax brackets, TIPS principal, or I-bond rates. Others are restated in today's dollars so different years can be compared: by the BLS consumer price index, $30,000 in 1985 bought about what $93,000 buys in 2026. ×DON'T TRUST, VERIFYClaim: S&P 500 long-term real (inflation-adjusted) return is approximately 7% annualized.Verify at: Portfolio Visualizer ↗ Source 1 in the list belowDepends on time window. Check the specific period you care about..

THAT PURCHASE COULD BE WORTH
$0
in 20 years at 7% annually
WHAT DOES THAT MEAN?

Image is generated on your device. Nothing is sent to any server.

Projection, not a promise. The result follows the assumptions you enter. Real results will differ, sometimes by a lot.

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 ×DON'T TRUST, VERIFYClaim: Historical Bitcoin returns are not a forecast.Verify at: CoinGecko historical ↗ Source 2 in the list belowVerify with your own start date and window..

A note on what this tool is and isn't

Compound interestcompound interestEarning interest on your interest. Your returns reinvested to earn even more returns over time.Full definition 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 for recurring amounts; one-time amounts compound annually.
  • Money is assumed invested consistently; in reality the amount "spent" happens continuously.
  • The "cash" line loses purchasing powerPurchasing powerWhat money can actually buy, not the number on the bill or in the account. Inflation shrinks it over time: by the BLS consumer price index, it takes more than $8 today to buy what $1 bought in 1971. Same dollar, much less buying ability.Full definition at a fixed 3.5%/yr, a long-run assumption near the ~3.9% CPIConsumer Price Index (CPI)The government's measure of how much a typical basket of consumer goods costs over time.Full definition average since 1971. It deliberately does not track the latest CPI print (3.35% for the 12 months through August 2026) because the chart projects decades forward, and a single hot or cold year shouldn't re-anchor a multi-decade line.
  • 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. The assumptions and default values behind the result are listed under “What this tool assumes” on this page. Verify the methodology or inspect the source code in your browser's dev tools.

Where to go from here

Read next

Lifestyle Inflation

When income rises, spending tends to rise with it. The mechanism, the math on $50K to $130K careers, and the half-and-half rule that breaks the pattern.

Explore further
  • Order of OperationsThe order to deploy each dollar: emergency fund, employer match, high-interest debt, HSA, Roth, then taxable.
  • NPV Decision CalculatorApplies net present value to three common decisions: paying off debt versus investing, taking a job offer, or a lump-sum investment with ongoing return.
  • Compound Interest VisualizerEnter a starting amount, monthly contribution, return rate, and years to see the compounding growth curve.

Sources

Verify badges in the text link to these sources. Figures, rates and rules change: check each source’s date before acting on it.

  1. Portfolio Visualizer ↩
  2. CoinGecko, CoinGecko historical data ↩

Calculators are educational estimates, not financial advice. Disclosures · How pages are reviewed