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How to calculate Rule of 72 (years to double)

The Rule of 72 (years to double) formula, with plain worked examples you can check yourself.

Rule of 72 (years to double) = 72 ÷ r

Worked examples

r = 4%Rule of 72 (years to double) = 18
r = 8%Rule of 72 (years to double) = 9
r = 9%Rule of 72 (years to double) = 8

How to use it

  1. Write down the values for each letter in the formula.
  2. Do the brackets first, then divide or multiply.
  3. Check the units before you compare results.
  4. Compare the answer with last period or with a competitor to see if it is good or bad.

This formula belongs to Money & Prices.

Related terms

InflationPrice elasticityDeflationMonetary policyMoney supplyCentral bank

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