How do you perform an accurate calculation of painting costs for a Bedroom in Biel, excluding ceilings, 2 doors, and 2 windows, with dimensions of 10m x 3m?

Performing an accurate calculation of painting costs for a Bedroom in Biel, excluding ceilings, 2 doors, and 2 windows, with dimensions of 10m x 3m, consider paying CHF 316.00.

*) The calculations are approximate, based on a room height of 2.4m, and include one coat of paint. The price covers only the labor, excluding any services or materials.