Finance Tools
Rule of 72 Calculator
Estimate how long it takes for an investment to double using the Rule of 72.
Years to double (Rule of 72)
9.00 years
Years to double (Exact)
9.01 years
Years to double (Rule of 69.3)
8.66 years
Required return (Rule of 72)
7.20%
Required return (Exact)
7.18%
Rule-72 error vs exact
-0.01y (-0.07%)
Rule of 72 formula: 72 / return %
Exact doubling formula: ln(2) / ln(1 + r) where r = return as decimal.
About
How it helps
The Rule of 72 is a shortcut for estimating how many years it takes an investment to double: Years to Double = 72 / Annual Return (%).
This calculator provides both the Rule of 72 estimate and the exact compound-growth estimate so you can quickly compare approximation vs precision.
It also solves the reverse question: if you want to double in a target number of years, what annual return is required under Rule of 72 and under exact compounding.
Use this for fast planning, screening, and scenario comparison. Final investment assumptions should still be validated with full cash-flow and risk modeling.
FAQ
Frequently Asked Questions
+What is the Rule of 72?
The Rule of 72 estimates years to double an investment by dividing 72 by the annual return percentage.
+Is Rule of 72 exact?
No. It is an approximation. The exact doubling-time formula is ln(2) / ln(1 + r), where r is the annual return as a decimal.
+How do I estimate required return for a target doubling period?
Use the reverse Rule of 72: Required Return (%) = 72 / Target Years. The calculator also shows the exact required return from compound-growth math.
Related
More Tools
Burn Rate Calculator
Calculate your startup's monthly burn rate and cash runway. Enter cash on hand, monthly revenue, and expenses to see how long your capital lasts.
Open ->Loan Calculator
Calculate monthly loan payments, total repayment, and total interest for any fixed-rate loan. Works for personal loans, car loans, and business loans.
Open ->Markup vs Margin Calculator
Compare markup and margin from cost and selling price to avoid pricing mistakes.
Open ->Mortgage Calculator
Calculate your monthly mortgage payment instantly. Enter home price, down payment, interest rate, and loan term to see total cost, total interest, and payoff date.
Open ->