Rule of 72 Calculator FAQ
What does the Rule of 72 tell me?
It gives a quick estimate of how many years it takes to double an investment at a fixed annual return. It can also work backwards to estimate the annual interest rate needed to double in a chosen number of years.
How accurate is the Rule of 72?
It is an approximation, not an exact compound-interest formula. It works best for rates that are not too far from common long-term returns, but it is still very useful for fast mental checks.
When should I use this calculator?
Use it when you want a fast answer to questions like how long to double money, what annual return is needed to double, or how different rates compare over time.
Is the Rule of 72 the same as compound interest?
No. The Rule of 72 is a shortcut built on compound growth. It gives a practical estimate, while exact doubling time comes from the full compound-interest calculation.
