Do The Money Math

Real Returns Calculator

What investing actually does — real S&P 500 history, crashes and all. Not a fake flat 7%.

I invest per month ($)

For this many years

You invested

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It became

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Your real return

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Worst drop

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Cost of Waiting

Three investors — same amount per month, but one started 30 years ago, one 20, one 10. The gap is staggering.

Monthly investment ($)

Started 30 years ago

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Started 20 years ago

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Started 10 years ago

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Cost of waiting 10y

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Lump Sum vs DCA

Got a windfall? Invest it all at once or spread it over 12 months? Real history decides.

Total amount ($)

Investment period (years)

Lump sum final

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DCA final

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Lump sum wins

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Best DCA advantage

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Credit Card Payoff

Minimum payments are a trap. See exactly how long it takes and how much you really pay.

Balance ($)

APR (%)

Min payment (%)

Months to payoff (min)

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Total paid (min)

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Total interest (min)

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Fixed payment saves

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Car Loan True Cost

The sticker price is a lie. See the real cost after interest and depreciation.

Car price ($)

Down payment ($)

APR (%)

Term (months)

Monthly payment

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Total paid

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Total interest

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True cost (w/ depreciation)

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Depreciation assumes ~15%/year (industry average). Actual varies by make/model.

Retirement Calculator

How much do you need? The 4% rule says your nest egg should be 25x your desired annual income.

Desired annual income ($)

Monthly savings ($)

Expected return (%/yr)

Target nest egg

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Years to reach it

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You'll invest

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Market does the rest

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Based on the 4% safe withdrawal rule (Trinity Study). Assumes consistent monthly contributions.

Salary Breakdown

Where does every dollar of your paycheck actually go? Federal tax, state tax, FICA — see the real take-home.

Gross salary ($)

State tax rate (%)

Federal tax

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State tax

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FICA (SS + Medicare)

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Take-home

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2026 federal brackets (single filer, standard deduction $15,700). FICA: 6.2% SS (up to $176,100) + 1.45% Medicare.

Inflation Calculator

What's your money really worth? See how inflation silently eats your purchasing power — real CPI data.

Amount ($)

Start year

Worth today

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Purchasing power lost

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Avg annual inflation

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Data: US CPI-U (Bureau of Labor Statistics via FRED). Shows what a fixed dollar amount can buy over time.

Debt vs Invest

Should you pay off debt or invest the extra money? The math is simpler than you think.

Extra money per month ($)

Debt APR (%)

Expected investment return (%)

Time horizon (years)

Debt interest saved

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Investment growth

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Net difference

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Break-even rate

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Simplified comparison: does not account for taxes on investment gains, which would favor debt payoff further.

See the full breakdowns on YouTube