What about windows and doors?
It is common practice to ignore openings when estimating drywall to account for wastage and cutting.
Walls: 384.0 sq ft. Ceiling: 144.0 sq ft. Total: 528.0 sq ft.
You need 19 standard 4x8 sheets. If using 4x12 sheets (48 sq ft), you would need approx 13 sheets.
Estimate approx 5-6 lbs of joint compound and 35-40 ft of tape per 100 sq ft of drywall. For this room: ~29 lbs mud, ~201 ft tape.
Sheets = Total Area / 32Wall AreaPerimeter x HeightCeiling AreaLength x WidthSheet Area32 sq ft (4x8)