The formula to calculate depreciation using the Double Rate Declining Balance Method is:

\[ C_m = Co (1 - \frac{2}{n})^m \]

Where:

• \(Co\) is the original cost.
• \(n\) is the useful life in years.
• \(m\) is the age of the property at any time less than \(n\).
• \(C_m\) is the book value at the end of \(m\) years.