Free calculator
Rule of 72 Calculator
Enter your annual rate of return and see exactly how long it takes your investment to double — plus a comparison across every common account type.
Enter a rate above to see your doubling time instantly.
Formula: 72 ÷ rate = years to double
How the Rule of 72 works
Divide 72 by your annual interest rate. The result is approximately how many years it takes to double your money at that rate, assuming compound interest.
Example: At 8% annual return, 72 ÷ 8 = 9 years to double. At 6%, it takes 12 years. At 12%, just 6 years. The math is simple — the implications are profound.
The rule also works in reverse on debt. A credit card at 24% doubles what you owe in 3 years. That's why eliminating high-interest debt is almost always the highest-return financial move available to you.
How common rates compare
The same $10,000 invested at different rates — see how dramatically the doubling time changes.
Want the full explanation?
Understand the formula, see real-world examples across every account type, and learn where the rule breaks down.
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The Rule of 72 is one lens. The Cube Wealth Readiness Engine™ evaluates your complete financial situation across 6 pillars — and maps exactly what to do next.
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