📄️ What Is the Rule of 72?
Discover the Rule of 72, a mental-math shortcut that estimates how long it takes to double your money through compound interest and investment growth.
📄️ The Math Behind the Rule of 72
Understand the mathematical derivation of the Rule of 72, from the compound interest formula to logarithms and why this approximation works so well.
📄️ Rule of 72 Worked Examples
Walk through realistic Rule of 72 worked examples for retirement planning, college savings, inflation impact, and investment comparisons with detailed calculations.
📄️ The Rule of 114 for Tripling Money
Discover the Rule of 114, which estimates how long it takes to triple your money through compound growth, extending the Rule of 72 to the next multiple.
📄️ The Rule of 144 for Quadrupling Money
Learn the Rule of 144, which estimates how long it takes to quadruple wealth through compound growth, completing the family of multiplication rules.
📄️ Rule of 69, Rule of 70
Discover rule of 69 and rule of 70 for precise doubling-time calculations across continuous and discrete compounding periods.
📄️ When the Rule Breaks Down
Explore where rule of 72 accuracy falters, from extreme interest rates to specific time horizons and when exact calculations matter most.
📄️ Rule of 72 and Inflation
Apply rule of 72 to inflation to understand purchasing power erosion and plan real returns, not nominal gains.
📄️ Rule of 72 and Debt
Apply rule of 72 to debt to understand how interest accrues on borrowed money, revealing the cost of leverage and credit.
📄️ Population and Economic Growth
Apply rule of 72 to economic growth and population dynamics, revealing how nations double wealth and demographics shape civilization.
📄️ Doubling-Time Table
Reference tables showing exact doubling times across interest rates from 1% to 20%, with calculations and practical applications for quick investment analysis.
📄️ Mental-Math Tricks
Master mental calculations for compound interest—dividing rates, counting doublings, and estimating wealth growth in real-time financial conversations.
📄️ Compare Investments
Compare bonds, stocks, and alternatives using Rule of 72—evaluating doubling times across fees, taxes, and horizons for data-driven investment decisions.
📄️ Common Pitfalls
Avoid 10+ critical errors that make Rule-of-72 estimates dangerously wrong—from ignoring inflation and taxes to misapplying the formula to risky assets.
📄️ Cheat Sheet
Instant reference guide with formulas, doubling tables, mental shortcuts, and decision trees for applying Rule of 72 calculations without a calculator.