The formulas to calculate the volume of paint needed are:

\[ Pv = \frac{3.78 \cdot Aw}{20} \quad \text{(1st coating)} \]

\[ Pv = \frac{3.78 \cdot Aw}{25} \quad \text{(2nd coating)} \]

Where:

• \(Pv\) is the volume of paint needed (liters).
• \(Aw\) is the area of the wall (m²).