Run the numbers from the video.
The math behind your money. Education, not advice.
Rule of 72: how long until your money doubles?
Divide 72 by the rate for a fast estimate, then check it against the exact math. The same clock runs for prices (inflation) and for card debt.
Open the calculatorCalculators
Each one opens with the numbers from its video. Then change them to yours.
Grow
Compounding, fees, inflation and the doubling clock.
Rule of 72 / doubling time
Divide 72 by the rate, then check it against the exact math.
Compound interest
Growth on growth, year by year.
Fee drag
Small percentages, big dollars.
Inflation doubling clock
The reverse doubling clock.
Average vs compounded return
Why the average can mislead.
Savings interest
What your APY really pays.
When interest beats deposits
The month your money out-earns you.
Monthly investing goal
Working backward from a number.
Dividend income
Yield in, income out.
Retire
Roth, 401(k), the match, ESPPs and starting later.
Roth IRA growth
Contributions vs growth, plus 2026 limits.
401(k) take-home cost
Pre-tax math for 2026.
Roth vs traditional 401(k)
Why the math is a tie.
Employer match
The instant 50%.
ESPP (employee stock purchase plan)
The discount, the lookback, the $25,000 cap.
Catch-up ladder
What starting later costs, in % of pay.
Retirement savings
Future dollars vs today's dollars.
Debt
Credit cards, payoff orders and student loans.
Minimum-payment trap
Minimums vs a fixed payment.
Avalanche vs snowball
Two payoff orders, side by side.
Daily card interest
APR ÷ 365, compounded.
Balance transfer
The fee, the promo, the cliff.
Student loan interest
Daily interest and amortization.
How we do the math
Steady, labeled rates
Returns are hypothetical and held steady so you can see the mechanics. Real returns jump around.
Sources shown
Rates and limits come from the IRS, the Federal Reserve, the FDIC and Federal Student Aid, with an "as of" date.
You can check it
Every result shows its formula with your numbers plugged in. More about us.